what is statistical problem solving

Teach yourself statistics

Statistics Problems

One of the best ways to learn statistics is to solve practice problems. These problems test your understanding of statistics terminology and your ability to solve common statistics problems. Each problem includes a step-by-step explanation of the solution.

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Problem description:

In one state, 52% of the voters are Republicans, and 48% are Democrats. In a second state, 47% of the voters are Republicans, and 53% are Democrats. Suppose a simple random sample of 100 voters are surveyed from each state.

What is the probability that the survey will show a greater percentage of Republican voters in the second state than in the first state?

The correct answer is C. For this analysis, let P 1 = the proportion of Republican voters in the first state, P 2 = the proportion of Republican voters in the second state, p 1 = the proportion of Republican voters in the sample from the first state, and p 2 = the proportion of Republican voters in the sample from the second state. The number of voters sampled from the first state (n 1 ) = 100, and the number of voters sampled from the second state (n 2 ) = 100.

The solution involves four steps.

• Make sure the sample size is big enough to model differences with a normal population. Because n 1 P 1 = 100 * 0.52 = 52, n 1 (1 - P 1 ) = 100 * 0.48 = 48, n 2 P 2 = 100 * 0.47 = 47, and n 2 (1 - P 2 ) = 100 * 0.53 = 53 are each greater than 10, the sample size is large enough.
• Find the mean of the difference in sample proportions: E(p 1 - p 2 ) = P 1 - P 2 = 0.52 - 0.47 = 0.05.

σ d = sqrt{ [ P1( 1 - P 1 ) / n 1 ] + [ P 2 (1 - P 2 ) / n 2 ] }

σ d = sqrt{ [ (0.52)(0.48) / 100 ] + [ (0.47)(0.53) / 100 ] }

σ d = sqrt (0.002496 + 0.002491) = sqrt(0.004987) = 0.0706

z p 1 - p 2 = (x - μ p 1 - p 2 ) / σ d = (0 - 0.05)/0.0706 = -0.7082

Using Stat Trek's Normal Distribution Calculator , we find that the probability of a z-score being -0.7082 or less is 0.24.

Therefore, the probability that the survey will show a greater percentage of Republican voters in the second state than in the first state is 0.24.

See also: Difference Between Proportions

Statistical Thinking for Industrial Problem Solving

A free online statistics course.

Back to Course Overview

Statistical Thinking and Problem Solving

Statistical thinking is vital for solving real-world problems. At the heart of statistical thinking is making decisions based on data. This requires disciplined approaches to identifying problems and the ability to quantify and interpret the variation that you observe in your data.

In this module, you will learn how to clearly define your problem and gain an understanding of the underlying processes that you will improve. You will learn techniques for identifying potential root causes of the problem. Finally, you will learn about different types of data and different approaches to data collection.

Estimated time to complete this module: 2 to 3 hours

Statistical Thinking and Problem Solving Overview (0:36)

Specific topics covered in this module include:

Statistical thinking.

• What is Statistical Thinking

Problem Solving

• Overview of Problem Solving
• Statistical Problem Solving
• Types of Problems
• Defining the Problem
• Goals and Key Performance Indicators
• The White Polymer Case Study

Defining the Process

• What is a Process?
• Developing a SIPOC Map
• Developing an Input/Output Process Map
• Top-Down and Deployment Flowcharts

Identifying Potential Root Causes

• Tools for Identifying Potential Causes
• Brainstorming
• Multi-voting
• Using Affinity Diagrams
• Cause-and-Effect Diagrams
• The Five Whys
• Cause-and-Effect Matrices

Compiling and Collecting Data

• Data Collection for Problem Solving
• Types of Data
• Operational Definitions
• Data Collection Strategies
• Importing Data for Analysis

What Is Statistics?

• First Online: 10 December 2017

Cite this chapter

• Christopher J. Wild 4 ,
• Jessica M. Utts 5 &
• Nicholas J. Horton 6  

Part of the book series: Springer International Handbooks of Education ((SIHE))

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What is statistics? We attempt to answer this question as it relates to grounding research in statistics education. We discuss the nature of statistics as the science of learning from data, its history and traditions, what characterizes statistical thinking and how it differs from mathematics, connections with computing and data science, why learning statistics is essential, and what is most important. Finally, we attempt to gaze into the future, drawing upon what is known about the fast-growing demand for statistical skills and the portents of where the discipline is heading, especially those arising from data science and the promises and problems of big data.

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Wild, C.J., Utts, J.M., Horton, N.J. (2018). What Is Statistics?. In: Ben-Zvi, D., Makar, K., Garfield, J. (eds) International Handbook of Research in Statistics Education. Springer International Handbooks of Education. Springer, Cham. https://doi.org/10.1007/978-3-319-66195-7_1

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Home / Six Sigma / The Six Sigma Approach: A Data-Driven Approach To Problem-Solving

The Six Sigma Approach: A Data-Driven Approach To Problem-Solving

If you are a project manager or an engineer, you may have heard of the  6 Sigma approach to problem-solving by now. In online Six Sigma courses that teach the Six Sigma principles , you will learn that a data-driven approach to problem-solving , or the Six Sigma approach, is a better way to approach problems. If you have a Six Sigma Green Belt certification then you will be able to turn practical problems into practical solutions using only facts and data.

Attend our 100% Online & Self-Paced Free Six Sigma Training .

This approach does not have room for gut feel or jumping to conclusions. However, if you are reading this article, you are probably still curious about the Six Sigma approach to problem-solving.

What is the Six Sigma Approach?

Let’s see what the Six Sigma approach or thinking is. As briefly described in free Six Sigma Green Belt Certification training , this approach is abbreviated as DMAIC. The DMAIC methodology of Six Sigma states that all processes can be Defined, Measured, Analyzed, Improved and Controlled . These are the phases in this approach. Collectively, it is called as DMAIC. Every Six Sigma project goes through these five stages. In the Define phase, the problem is looked at from several perspectives to identify the scope of the problem. All possible inputs in the process that may be causing the problem are compared and the critical few are identified. These inputs are Measured and Analyzed to determine whether they are the root cause of the problem. Once the root cause has been identified, the problem can be fixed or Improved. After the process has been improved, it must be controlled to ensure that the problem has been fixed in the long-term.

Check our Six Sigma Training Video

Every output (y) is a function of one or multiple inputs (x)

Any process which has inputs (X), and delivers outputs (Y) comes under the purview of the Six Sigma approach. X may represent an input, cause or problem, and Y may represent output, effect or symptom . We can say here that controlling inputs will control outputs. Because the output Y will be generated based on the inputs X.

This Six Sigma approach is called Y=f(X) thinking. It is the mechanism of the Six Sigma. Every problematic situation has to be converted into this equation. It may look difficult but it is just a new way of looking at the problem.

Please remember that the context of relating X and Y to each other would vary from situation to situation. If X is your input, then only Y becomes your output. If X is your cause, Y will not be regarded as the output. If X is your input, Y cannot be called as an effect.

Let’s go further. The equation of Y=f(X) could involve several subordinate outputs, perhaps as leading indicators of the overall “Big Y.” For example, if TAT was identified as the Big Y, the improvement team may examine leading indicators, such as Cycle Time; Lead Time as little Ys. Each subordinate Y may flow down into its own Y= f(X) relationship wherein some of the critical variables for one also may affect another little Y. That another little variable could be your potential X or critical X.

A practical vs. a statistical problem and solution

In the Six Sigma approach, the practical problem is the problem or pain area which has been persisting on your production or shop floor. You will need to c onvert this practical problem into a statistical problem. A statistical problem is the problem that is addressed with facts and data analysis methods. Just a reminder, the measurement, and analysis of a statistical problem is completed in Measure and Analyze phase of the Six Sigma approach or DMAIC.

In this approach, the statistical problem will then be converted into a statistical solution. It is the solution with a known confidence or risk levels versus an “I think” solution. This solution is not based on gut feeling. It’s a completely data-driven solution because it was found using the Six Sigma approach.

A Six Sigma approach of DMAIC project would assist you to convert your Practical Problem into Statistical Problem and then your Statistical Problem into Statistical Solution. The same project would also give you the Practical Solutions that aren’t complex and too difficult to implement. That’s how the Six Sigma approach works.

This approach may seem like a lot of work. Wouldn’t it be better to guess what the problem is and work on it from there? That would certainly be easier, but consider that randomly choosing a root cause of a problem may lead to hard work that doesn’t solve the problem permanently. You may be working to create a solution that will only fix 10% of the problem while following the Six Sigma approach will help you to identify the true root cause of the problem . Using this data-driven Six Sigma approach, you will only have to go through the problem-solving process once.

The Six Sigma approach is a truly powerful problem-solving tool. By working from a practical problem to a statistical problem, a statistical solution and finally a practical solution, you will be assured that you have identified the correct root cause of the problem which affects the quality of your products. The Six Sigma approach follows a standard approach – DMAIC – that helps the problem-solver to convert the practical problem into a practical solution based on facts and data . It’s very important to note that the Six Sigma approach is not a one-man show. Problem solving should be approached as a team with subject matter experts and decicion makers involved.

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Statistical Problem Solving (SPS)

• Statistical Problem Solving

Problem solving in any organization is a problem. Nobody wants to own the responsibility for a problem and that is the reason, when a problem shows up fingers may be pointing at others rather than self.

This is a natural human instinctive defense mechanism and hence cannot hold it against any one. However, it is to be realized the problems in industry are real and cannot be wished away, solution must be sought either by hunch or by scientific methods. Only a systematic disciplined approach for defining and solving problems consistently and effectively reveal the real nature of a problem and the best possible solutions .

A Chinese proverb says, “ it is cheap to do guesswork for solution, but a wrong guess can be very expensive”. This is to emphasize that although occasional success is possible trough hunches gained through long years of experience in doing the same job, but a lasting solution is possible only through scientific methods.

One of the major scientific method for problem solving is through Statistical Problem Solving (SPS) this method is aimed at not only solving problems but may be used for improvement on existing situation. It involves a team armed with process and product knowledge, having willingness to work together as a team, can undertake selection of some statistical methods, have willingness to adhere to principles of economy and willingness to learn along the way.

Statistical Problem Solving (SPS) could be used for process control or product control. In many situations, the product would be customer dictated, tried, tested and standardized in the facility may involve testing at both internal to facility or external to facility may be complex and may require customer approval for changes which could be time consuming and complex. But if the problem warrants then this should be taken up. 

Process controls are lot simpler than product control where SPS may be used effectively for improving profitability of the industry, by reducing costs and possibly eliminating all 7 types of waste through use of Kaizen and lean management techniques.

The following could be used as 7 steps for Statistical Problem Solving (SPS)

• Defining the problem
• Listing variables
• Prioritizing variables
• Evaluating top few variables
• Optimizing variable settings
• Monitor and Measure results
• Reward/Recognize Team members

Defining the problem: Source for defining the problem could be from customer complaints, in-house rejections, observations by team lead or supervisor or QC personnel, levels of waste generated or such similar factors.

Listing and prioritizing variables involves all features associated with the processes. Example temperature, feed and speed of the machine, environmental factors, operator skills etc. It may be difficult to try and find solution for all variables together. Hence most probable variables are to be selected based on collective wisdom and experience of the team attempting to solve the problem.

Collection of data: Most common method in collecting data is the X bar and R charts.  Time is used as the variable in most cases and plotted on X axis, and other variables such as dimensions etc. are plotted graphically as shown in example below.

Once data is collected based on probable list of variables, then the data is brought to the attention of the team for brainstorming on what variables are to be controlled and how solution could be obtained. In other words , optimizing variables settings . Based on the brainstorming session process control variables are evaluated using popular techniques like “5 why”, “8D”, “Pareto Analysis”, “Ishikawa diagram”, “Histogram” etc. The techniques are used to limit variables and design the experiments and collect data again. Values of variables are identified from data which shows improvement. This would lead to narrowing down the variables and modify the processes, to achieve improvement continually. The solutions suggested are to be implemented and results are to be recorded. This data is to be measured at varying intervals to see the status of implementation and the progress of improvement is to be monitored till the suggested improvements become normal routine. When results indicate resolution of problem and the rsults are consistent then Team memebres are to be rewarded and recognized to keep up their morale for future projects.

Who Should Pursue SPS

• Statistical Problem Solving can be pursued by a senior leadership group for example group of quality executives meeting weekly to review quality issues, identify opportunities for costs saving and generate ideas for working smarter across the divisions
• Statistical Problem solving can equally be pursued by a staff work group within an institution that possesses a diversity of experience that can gather data on various product features and tabulate them statistically for drawing conclusions
• The staff work group proposes methods for rethinking and reworking models of collaboration and consultation at the facility
• The senior leadership group and staff work group work in partnership with university faculty and staff to identify research communications and solve problems across the organization

Benefits of Statistical Problem Solving

• Long term commitment to organizations and companies to work smarter.
• Reduces costs, enhances services and increases revenues.
• Mitigating the impact of budget reductions while at the same time reducing operational costs.
• Improving operations and processes, resulting in a more efficient, less redundant organization.
• Promotion of entrepreneurship intelligence, risk taking corporations and engagement across interactions with business and community partners.
• A culture change in a way a business or organization collaborates both internally and externally.
• Identification and solving of problems.
• Helps to repetition of problems
• Meets the mandatory requirement for using scientific methods for problem solving
• Savings in revenue by reducing quality costs
• Ultimate improvement in Bottom -Line
• Improvement in teamwork and morale in working
• Improvement in overall problem solving instead of harping on accountability

Business Impact

• Scientific data backed up problem solving techniques puts the business at higher pedestal in the eyes of the customer.
• Eradication of over consulting within businesses and organizations which may become a pitfall especially where it affects speed of information.
• Eradication of blame game

QSE’s Approach to Statistical Problem Solving

By leveraging vast experience, it has, QSE organizes the entire implementation process for Statistical Problem Solving in to Seven simple steps

• Define the Problem
• List Suspect Variables
• Prioritize Selected Variables
• Evaluate Critical Variables
• Optimize Critical Variables
• Monitor and Measure Results
• Reward/Recognize Team Members
• Define the Problem (Vital Few -Trivial Many):

List All the problems which may be hindering Operational Excellence . Place them in a Histogram under as many categories as required.

Select Problems based on a simple principle of Vital Few that is select few problems which contribute to most deficiencies within the facility

QSE advises on how to Use X and R Charts to gather process data.

• List Suspect Variables:

QSE Advises on how to gather data for the suspect variables involving cross functional teams and available past data

• Prioritize Selected Variables Using Cause and Effect Analysis:

QSE helps organizations to come up prioritization of select variables that are creating the problem and the effect that are caused by them. The details of this exercise are to be represented in the Fishbone Diagram or Ishikawa Diagram

• Evaluate Critical Variables:

Use Brain Storming method to use critical variables for collecting process data and Incremental Improvement for each selected critical variable

QSE with its vast experiences guides and conducts brain storming sessions in the facility to identify KAIZEN (Small Incremental projects) to bring in improvements. Create a bench mark to be achieved through the suggested improvement projects

• Optimize Critical Variable Through Implementing the Incremental Improvements:

QSE helps facilities to implement incremental improvements and gather data to see the results of the efforts in improvements

• Monitor and Measure to Collect Data on Consolidated incremental achievements :

Consolidate and make the major change incorporating all incremental improvements and then gather data again to see if the benchmarks have been reached

QSE educates and assists the teams on how these can be done in a scientific manner using lean and six sigma techniques

QSE organizes verification of Data to compare the results from the original results at the start of the projects. Verify if the suggestions incorporated are repeatable for same or better results as planned

              Validate the improvement project by multiple repetitions

• Reward and Recognize Team Members:

QSE will provide all kinds of support in identifying the great contributors to the success of the projects and make recommendation to the Management to recognize the efforts in a manner which befits the organization to keep up the morale of the contributors.

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ISO Standards

• ISO 9001:2015
• ISO 10993-1:2018
• ISO 13485:2016
• ISO 14001:2015
• ISO 15189:2018
• ISO 15190:2020
• ISO 15378:2017
• ISO/IEC 17020:2012
• ISO/IEC 17025:2017
• ISO 20000-1:2018
• ISO 22000:2018
• ISO 22301:2019
• ISO 27001:2015
• ISO 27701:2019
• ISO 28001:2007
• ISO 37001:2016
• ISO 45001:2018
• ISO 50001:2018
• ISO 55001:2014

Telecommunication Standards

• TL 9000 Version 6.1

Automotive Standards

• IATF 16949:2016
• ISO/SAE 21434:2021

Aerospace Standards

Forestry standards.

• FSC - Forest Stewardship Council
• PEFC - Program for the Endorsement of Forest Certification
• SFI - Sustainable Forest Initiative

Steel Construction Standards

Food safety standards.

• FDA Gluten Free Labeling & Certification
• Hygeine Excellence & Sanitation Excellence

GFSI Recognized Standards

• BRC Version 9
• FSSC 22000:2019
• Hygeine Excellent & Sanitation Excellence
• IFS Version 7
• SQF Edition 9
• All GFSI Recognized Standards for Packaging Industries

Problem Solving Tools

• Corrective & Preventative Actions
• Root Cause Analysis
• Supplier Development

Excellence Tools

• Bottom Line Improvement
• Customer Satisfaction Measurement
• Document Simplification
• Hygiene Excellence & Sanitation
• Lean & Six Sigma
• Malcom Baldridge National Quality Award
• Operational Excellence
• Safety (including STOP and OHSAS 45001)
• Sustainability (Reduce, Reuse, & Recycle)
• Total Productive Maintenance

Other Standards

• California Transparency Act
• Global Organic Textile Standard (GOTS)
• Hemp & Cannabis Management Systems
• Recycling & Re-Using Electronics
• ESG - Environmental, Social & Governance
• CDFA Proposition 12 Animal Welfare

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ORIGINAL RESEARCH article

Statistical analysis of complex problem-solving process data: an event history analysis approach.

• 1 Department of Statistics, London School of Economics and Political Science, London, United Kingdom
• 2 School of Statistics, University of Minnesota, Minneapolis, MN, United States
• 3 Department of Statistics, Columbia University, New York, NY, United States

Complex problem-solving (CPS) ability has been recognized as a central 21st century skill. Individuals' processes of solving crucial complex problems may contain substantial information about their CPS ability. In this paper, we consider the prediction of duration and final outcome (i.e., success/failure) of solving a complex problem during task completion process, by making use of process data recorded in computer log files. Solving this problem may help answer questions like “how much information about an individual's CPS ability is contained in the process data?,” “what CPS patterns will yield a higher chance of success?,” and “what CPS patterns predict the remaining time for task completion?” We propose an event history analysis model for this prediction problem. The trained prediction model may provide us a better understanding of individuals' problem-solving patterns, which may eventually lead to a good design of automated interventions (e.g., providing hints) for the training of CPS ability. A real data example from the 2012 Programme for International Student Assessment (PISA) is provided for illustration.

1. Introduction

Complex problem-solving (CPS) ability has been recognized as a central 21st century skill of high importance for several outcomes including academic achievement ( Wüstenberg et al., 2012 ) and workplace performance ( Danner et al., 2011 ). It encompasses a set of higher-order thinking skills that require strategic planning, carrying out multi-step sequences of actions, reacting to a dynamically changing system, testing hypotheses, and, if necessary, adaptively coming up with new hypotheses. Thus, there is almost no doubt that an individual's problem-solving process data contain substantial amount of information about his/her CPS ability and thus are worth analyzing. Meaningful information extracted from CPS process data may lead to better understanding, measurement, and even training of individuals' CPS ability.

Problem-solving process data typically have a more complex structure than that of panel data which are traditionally more commonly encountered in statistics. Specifically, individuals may take different strategies toward solving the same problem. Even for individuals who take the same strategy, their actions and time-stamps of the actions may be very different. Due to such heterogeneity and complexity, classical regression and multivariate data analysis methods cannot be straightforwardly applied to CPS process data.

Possibly due to the lack of suitable analytic tools, research on CPS process data is limited. Among the existing works, none took a prediction perspective. Specifically, Greiff et al. (2015) presented a case study, showcasing the strong association between a specific strategic behavior (identified by expert knowledge) in a CPS task from the 2012 Programme for International Student Assessment (PISA) and performance both in this specific task and in the overall PISA problem-solving score. He and von Davier (2015 , 2016) proposed an N-gram method from natural language processing for analyzing problem-solving items in technology-rich environments, focusing on identifying feature sequences that are important to task completion. Vista et al. (2017) developed methods for the visualization and exploratory analysis of students' behavioral pathways, aiming to detect action sequences that are potentially relevant for establishing particular paths as meaningful markers of complex behaviors. Halpin and De Boeck (2013) and Halpin et al. (2017) adopted a Hawkes process approach to analyzing collaborative problem-solving items, focusing on the psychological measurement of collaboration. Xu et al. (2018) proposed a latent class model that analyzes CPS patterns by classifying individuals into latent classes based on their problem-solving processes.

In this paper, we propose to analyze CPS process data from a prediction perspective. As suggested in Yarkoni and Westfall (2017) , an increased focus on prediction can ultimately lead us to greater understanding of human behavior. Specifically, we consider the simultaneous prediction of the duration and the final outcome (i.e., success/failure) of solving a complex problem based on CPS process data. Instead of a single prediction, we hope to predict at any time during the problem-solving process. Such a data-driven prediction model may bring us insights about individuals' CPS behavioral patterns. First, features that contribute most to the prediction may correspond to important strategic behaviors that are key to succeeding in a task. In this sense, the proposed method can be used as an exploratory data analysis tool for extracting important features from process data. Second, the prediction accuracy may also serve as a measure of the strength of the signal contained in process data that reflects one's CPS ability, which reflects the reliability of CPS tasks from a prediction perspective. Third, for low stake assessments, the predicted chance of success may be used to give partial credits when scoring task takers. Fourth, speed is another important dimension of complex problem solving that is closely associated with the final outcome of task completion ( MacKay, 1982 ). The prediction of the duration throughout the problem-solving process may provide us insights on the relationship between the CPS behavioral patterns and the CPS speed. Finally, the prediction model also enables us to design suitable interventions during their problem-solving processes. For example, a hint may be provided when a student is predicted having a high chance to fail after sufficient efforts.

More precisely, we model the conditional distribution of duration time and final outcome given the event history up to any time point. This model can be viewed as a special event history analysis model, a general statistical framework for analyzing the expected duration of time until one or more events happen (see e.g., Allison, 2014 ). The proposed model can be regarded as an extension to the classical regression approach. The major difference is that the current model is specified over a continuous-time domain. It consists of a family of conditional models indexed by time, while the classical regression approach does not deal with continuous-time information. As a result, the proposed model supports prediction at any time during one's problem-solving process, while the classical regression approach does not. The proposed model is also related to, but substantially different from response time models (e.g., van der Linden, 2007 ) which have received much attention in psychometrics in recent years. Specifically, response time models model the joint distribution of response time and responses to test items, while the proposed model focuses on the conditional distribution of CPS duration and final outcome given the event history.

Although the proposed method learns regression-type models from data, it is worth emphasizing that we do not try to make statistical inference, such as testing whether a specific regression coefficient is significantly different from zero. Rather, the selection and interpretation of the model are mainly justified from a prediction perspective. This is because statistical inference tends to draw strong conclusions based on strong assumptions on the data generation mechanism. Due to the complexity of CPS process data, a statistical model may be severely misspecified, making valid statistical inference a big challenge. On the other hand, the prediction framework requires less assumptions and thus is more suitable for exploratory analysis. More precisely, the prediction framework admits the discrepancy between the underlying complex data generation mechanism and the prediction model ( Yarkoni and Westfall, 2017 ). A prediction model aims at achieving a balance between the bias due to this discrepancy and the variance due to a limited sample size. As a price, findings from the predictive framework are preliminary and only suggest hypotheses for future confirmatory studies.

The rest of the paper is organized as follows. In Section 2, we describe the structure of complex problem-solving process data and then motivate our research questions, using a CPS item from PISA 2012 as an example. In Section 3, we formulate the research questions under a statistical framework, propose a model, and then provide details of estimation and prediction. The introduced model is illustrated through an application to an example item from PISA 2012 in Section 4. We discuss limitations and future directions in Section 5.

2. Complex Problem-Solving Process Data

2.1. a motivating example.

We use a specific CPS item, CLIMATE CONTROL (CC) 1 , to demonstrate the data structure and to motivate our research questions. It is part of a CPS unit in PISA 2012 that was designed under the “MicroDYN” framework ( Greiff et al., 2012 ; Wüstenberg et al., 2012 ), a framework for the development of small dynamic systems of causal relationships for assessing CPS.

In this item, students are instructed to manipulate the panel (i.e., to move the top, central, and bottom control sliders; left side of Figure 1A ) and to answer how the input variables (control sliders) are related to the output variables (temperature and humidity). Specifically, the initial position of each control slider is indicated by a triangle “▴.” The students can change the top, central and bottom controls on the left of Figure 1 by using the sliders. By clicking “APPLY,” they will see the corresponding changes in temperature and humidity. After exploration, the students are asked to draw lines in a diagram ( Figure 1B ) to answer what each slider controls. The item is considered correctly answered if the diagram is correctly completed. The problem-solving process for this item is that the students must experiment to determine which controls have an impact on temperature and which on humidity, and then represent the causal relations by drawing arrows between the three inputs (top, central, and bottom control sliders) and the two outputs (temperature and humidity).

Figure 1. (A) Simulation environment of CC item. (B) Answer diagram of CC item.

PISA 2012 collected students' problem-solving process data in computer log files, in the form of a sequence of time-stamped events. We illustrate the structure of data in Table 1 and Figure 2 , where Table 1 tabulates a sequence of time-stamped events from a student and Figure 2 visualizes the corresponding event time points on a time line. According to the data, 14 events were recorded between time 0 (start) and 61.5 s (success). The first event happened at 29.5 s that was clicking “APPLY” after the top, central, and bottom controls were set at 2, 0, and 0, respectively. A sequence of actions followed the first event and finally at 58, 59.1, and 59.6 s, a final answer was correctly given using the diagram. It is worth clarifying that this log file does not collect all the interactions between a student and the simulated system. That is, the status of the control sliders is only recorded in the log file, when the “APPLY” button is clicked.

Table 1 . An example of computer log file data from CC item in PISA 2012.

Figure 2 . Visualization of the structure of process data from CC item in PISA 2012.

The process data for solving a CPS item typically have two components, knowledge acquisition and knowledge application, respectively. This CC item mainly focuses the former, which includes learning the causal relationships between the inputs and the outputs and representing such relationships by drawing the diagram. Since data on representing the causal relationship is relatively straightforward, in the rest of the paper, we focus on the process data related to knowledge acquisition and only refer a student's problem-solving process to his/her process of exploring the air conditioner, excluding the actions involving the answer diagram.

Intuitively, students' problem-solving processes contain information about their complex problem-solving ability, whether in the context of the CC item or in a more general sense of dealing with complex tasks in practice. However, it remains a challenge to extract meaningful information from their process data, due to the complex data structure. In particular, the occurrences of events are heterogeneous (i.e., different people can have very different event histories) and unstructured (i.e., there is little restriction on the order and time of the occurrences). Different students tend to have different problem-solving trajectories, with different actions taken at different time points. Consequently, time series models, which are standard statistical tools for analyzing dynamic systems, are not suitable here.

2.2. Research Questions

We focus on two specific research questions. Consider an individual solving a complex problem. Given that the individual has spent t units of time and has not yet completed the task, we would like to ask the following two questions based on the information at time t : How much additional time does the individual need? And will the individual succeed or fail upon the time of task completion?

Suppose we index the individual by i and let T i be the total time of task completion and Y i be the final outcome. Moreover, we denote H i ( t ) = ( h i 1 ( t ) , ... , h i p ( t ) ) ⊤ as a p -vector function of time t , summarizing the event history of individual i from the beginning of task to time t . Each component of H i ( t ) is a feature constructed from the event history up to time t . Taking the above CC item as an example, components of H i ( t ) may be, the number of actions a student has taken, whether all three control sliders have been explored, the frequency of using the reset button, etc., up to time t . We refer to H i ( t ) as the event history process of individual i . The dimension p may be high, depending on the complexity of the log file.

With the above notation, the two questions become to simultaneously predict T i and Y i based on H i ( t ). Throughout this paper, we focus on the analysis of data from a single CPS item. Extensions of the current framework to multiple-item analysis are discussed in Section 5.

3. Proposed Method

3.1. a regression model.

We now propose a regression model to answer the two questions raised in Section 2.2. We specify the marginal conditional models of Y i and T i given H i ( t ) and T i > t , respectively. Specifically, we assume

where Φ is the cumulative distribution function of a standard normal distribution. That is, Y i is assumed to marginally follow a probit regression model. In addition, only the conditional mean and variance are assumed for log( T i − t ). Our model parameters include the regression coefficients B = ( b jk )2 × p and conditional variance σ 2 . Based on the above model specification, a pseudo-likelihood function will be devived in Section 3.3 for parameter estimation.

Although only marginal models are specified, we point out that the model specifications (1) through (3) impose quite strong assumptions. As a result, the model may not most closely approximate the data-generating process and thus a bias is likely to exist. On the other hand, however, it is a working model that leads to reasonable prediction and can be used as a benchmark model for this prediction problem in future investigations.

We further remark that the conditional variance of log( T i − t ) is time-invariant under the current specification, which can be further relaxed to be time-dependent. In addition, the regression model for response time is closely related to the log-normal model for response time analysis in psychometrics (e.g., van der Linden, 2007 ). The major difference is that the proposed model is not a measurement model disentangling item and person effects on T i and Y i .

3.2. Prediction

Under the model in Section 3.1, given the event history, we predict the final outcome based on the success probability Φ( b 11 h i 1 ( t ) + ⋯ + b 1 p h ip ( t )). In addition, based on the conditional mean of log( T i − t ), we predict the total time at time t by t + exp( b 21 h i 1 ( t ) + ⋯ + b 2 p h ip ( t )). Given estimates of B from training data, we can predict the problem-solving duration and final outcome at any t for an individual in the testing sample, throughout his/her entire problem-solving process.

3.3. Parameter Estimation

It remains to estimate the model parameters based on a training dataset. Let our data be (τ i , y i ) and { H i ( t ): t ≥ 0}, i = 1, …, N , where τ i and y i are realizations of T i and Y i , and { H i ( t ): t ≥ 0} is the entire event history.

We develop estimating equations based on a pseudo likelihood function. Specifically, the conditional distribution of Y i given H i ( t ) and T i > t can be written as

where b 2 = ( b 11 , ... , b 1 p ) ⊤ . In addition, using the log-normal model as a working model for T i − t , the corresponding conditional distribution of T i can be written as

where b 2 = ( b 21 , ... , b 2 p ) ⊤ . The pseudo-likelihood is then written as

where t 1 , …, t J are J pre-specified grid points that spread out over the entire time spectrum. The choice of the grid points will be discussed in the sequel. By specifying the pseudo-likelihood based on the sequence of time points, the prediction at different time is taken into accounting in the estimation. We estimate the model parameters by maximizing the pseudo-likelihood function L ( B , σ).

In fact, (5) can be factorized into

Therefore, b 1 is estimated by maximizing L 1 ( b 1 ), which takes the form of a likelihood function for probit regression. Similarly, b 2 and σ are estimated by maximizing L 2 ( b 2 , σ), which is equivalent to solving the following estimation equations,

The estimating equations (8) and (9) can also be derived directly based on the conditional mean and variance specification of log( T i − t ). Solving these equations is equivalent to solving a linear regression problem, and thus is computationally easy.

3.4. Some Remarks

We provide a few remarks. First, choosing suitable features into H i ( t ) is important. The inclusion of suitable features not only improves the prediction accuracy, but also facilitates the exploratory analysis and interpretation of how behavioral patterns affect CPS result. If substantive knowledge about a CPS task is available from cognition theory, one may choose features that indicate different strategies toward solving the task. Otherwise, a data-driven approach may be taken. That is, one may select a model from a candidate list based on certain cross-validation criteria, where, if possible, all reasonable features should be consider as candidates. Even when a set of features has been suggested by cognition theory, one can still take the data-driven approach to find additional features, which may lead to new findings.

Second, one possible extension of the proposed model is to allow the regression coefficients to be a function of time t , whereas they are independent of time under the current model. In that case, the regression coefficients become functions of time, b jk ( t ). The current model can be regarded as a special case of this more general model. In particular, if b jk ( t ) has high variation along time in the best predictive model, then simply applying the current model may yield a high bias. Specifically, in the current estimation procedure, a larger grid point tends to have a smaller sample size and thus contributes less to the pseudo-likelihood function. As a result, a larger bias may occur in the prediction at a larger time point. However, the estimation of the time-dependent coefficient is non-trivial. In particular, constraints should be imposed on the functional form of b jk ( t ) to ensure a certain level of smoothness over time. As a result, b jk ( t ) can be accurately estimated using information from a finite number of time points. Otherwise, without any smoothness assumptions, to predict at any time during one's problem-solving process, there are an infinite number of parameters to estimate. Moreover, when a regression coefficient is time-dependent, its interpretation becomes more difficult, especially if the sign changes over time.

Third, we remark on the selection of grid points in the estimation procedure. Our model is specified in a continuous time domain that supports prediction at any time point in a continuum during an individual's problem-solving process. The use of discretized grid points is a way to approximate the continuous-time system, so that estimation equations can be written down. In practice, we suggest to place the grid points based on the quantiles of the empirical distribution of duration based on the training set. See the analysis in Section 4 for an illustration. The number of grid points may be further selected by cross validation. We also point out that prediction can be made at any time point on the continuum, not limited to the grid points for parameter estimation.

4. An Example from PISA 2012

4.1. background.

In what follows, we illustrate the proposed method via an application to the above CC item 2 . This item was also analyzed in Greiff et al. (2015) and Xu et al. (2018) . The dataset was cleaned from the entire released dataset of PISA 2012. It contains 16,872 15-year-old students' problem-solving processes, where the students were from 42 countries and economies. Among these students, 54.5% answered correctly. On average, each student took 129.9 s and 17 actions solving the problem. Histograms of the students' problem-solving duration and number of actions are presented in Figure 3 .

Figure 3. (A) Histogram of problem-solving duration of the CC item. (B) Histogram of the number of actions for solving the CC item.

4.2. Analyses

The entire dataset was randomly split into training and testing sets, where the training set contains data from 13,498 students and the testing set contains data from 3,374 students. A predictive model was built solely based on the training set and then its performance was evaluated based on the testing set. We used J = 9 grid points for the parameter estimation, with t 1 through t 9 specified to be 64, 81, 94, 106, 118, 132, 149, 170, and 208 s, respectively, which are the 10% through 90% quantiles of the empirical distribution of duration. As discussed earlier, the number of grid points and their locations may be further engineered by cross validation.

4.2.1. Model Selection

We first build a model based on the training data, using a data-driven stepwise forward selection procedure. In each step, we add one feature into H i ( t ) that leads to maximum increase in a cross-validated log-pseudo-likelihood, which is calculated based on a five-fold cross validation. We stop adding features into H i ( t ) when the cross-validated log-pseudo-likelihood stops increasing. The order in which the features are added may serve as a measure of their contribution to predicting the CPS duration and final outcome.

The candidate features being considered for model selection are listed in Table 2 . These candidate features were chosen to reflect students' CPS behavioral patterns from different aspects. In what follows, we discuss some of them. For example, the feature I i ( t ) indicates whether or not all three control sliders have been explored by simple actions (i.e., moving one control slider at a time) up to time t . That is, I i ( t ) = 1 means that the vary-one-thing-at-a-time (VOTAT) strategy ( Greiff et al., 2015 ) has been taken. According to the design of the CC item, the VOTAT strategy is expected to be a strong predictor of task success. In addition, the feature N i ( t )/ t records a student's average number of actions per unit time. It may serve as a measure of the student's speed of taking actions. In experimental psychology, response time or equivalently speed has been a central source for inferences about the organization and structure of cognitive processes (e.g., Luce, 1986 ), and in educational psychology, joint analysis of speed and accuracy of item response has also received much attention in recent years (e.g., van der Linden, 2007 ; Klein Entink et al., 2009 ). However, little is known about the role of speed in CPS tasks. The current analysis may provide some initial result on the relation between a student's speed and his/her CPS performance. Moreover, the features defined by the repeating of previously taken actions may reflect students' need of verifying the derived hypothesis on the relation based on the previous action or may be related to students' attention if the same actions are repeated many times. We also include 1, t, t 2 , and t 3 in H i ( t ) as the initial set of features to capture the time effect. For simplicity, country information is not taken into account in the current analysis.

Table 2 . The list of candidate features to be incorporated into the model.

Our results on model selection are summarized in Figure 4 and Table 3 . The pseudo-likelihood stopped increasing after 11 steps, resulting a final model with 15 components in H i ( t ). As we can see from Figure 4 , the increase in the cross-validated log-pseudo-likelihood is mainly contributed by the inclusion of features in the first six steps, after which the increment is quite marginal. As we can see, the first, second, and sixth features entering into the model are all related to taking simple actions, a strategy known to be important to this task (e.g., Greiff et al., 2015 ). In particular, the first feature being selected is I i ( t ), which confirms the strong effect of the VOTAT strategy. In addition, the third and fourth features are both based on N i ( t ), the number of actions taken before time t . Roughly, the feature 1 { N i ( t )>0} reflects the initial planning behavior ( Eichmann et al., 2019 ). Thus, this feature tends to measure students' speed of reading the instruction of the item. As discussed earlier, the feature N i ( t )/ t measures students' speed of taking actions. Finally, the fifth feature is related to the use of the RESET button.

Figure 4 . The increase in the cross-validated log-pseudo-likelihood based on a stepwise forward selection procedure. (A–C) plot the cross-validated log-pseudo-likelihood, corresponding to L ( B , σ), L 1 ( b 1 ), L 2 ( b 2 , σ), respectively.

Table 3 . Results on model selection based on a stepwise forward selection procedure.

4.2.2. Prediction Performance on Testing Set

We now look at the prediction performance of the above model on the testing set. The prediction performance was evaluated at a larger set of time points from 19 to 281 s. Instead of reporting based on the pseudo-likelihood function, we adopted two measures that are more straightforward. Specifically, we measured the prediction of final outcome by the Area Under the Curve (AUC) of the predicted Receiver Operating Characteristic (ROC) curve. The value of AUC is between 0 and 1. A larger AUC value indicates better prediction of the binary final outcome, with AUC = 1 indicating perfect prediction. In addition, at each time point t , we measured the prediction of duration based on the root mean squared error (RMSE), defined as

where τ i , i = N + 1, …, N + n , denotes the duration of students in the testing set, and τ ^ i ( t ) denotes the prediction based on information up to time t according to the trained model.

Results are presented in Figure 5 , where the testing AUC and RMSE for the final outcome and duration are presented. In particular, results based on the model selected by cross validation ( p = 15) and the initial model ( p = 4, containing the initial covariates 1, t , t 2 , and t 3 ) are compared. First, based on the selected model, the AUC is never above 0.8 and the RMSE is between 53 and 64 s, indicating a low signal-to-noise ratio. Second, the students' event history does improve the prediction of final outcome and duration upon the initial model. Specifically, since the initial model does not take into account the event history, it predicts the students with duration longer than t to have the same success probability. Consequently, the test AUC is 0.5 at each value of t , which is always worse than the performance of the selected model. Moreover, the selected model always outperforms the initial model in terms of the prediction of duration. Third, the AUC for the prediction of the final outcome is low when t is small. It keeps increasing as time goes on and fluctuates around 0.72 after about 120 s.

Figure 5 . A comparison of prediction accuracy between the model selected by cross validation and a baseline model without using individual specific event history.

4.2.3. Interpretation of Parameter Estimates

To gain more insights into how the event history affects the final outcome and duration, we further look at the results of parameter estimation. We focus on a model whose event history H i ( t ) includes the initial features and the top six features selected by cross validation. This model has similar prediction accuracy as the selected model according to the cross-validation result in Figure 4 , but contains less features in the event history and thus is easier to interpret. Moreover, the parameter estimates under this model are close to those under the cross-validation selected model, and the signs of the regression coefficients remain the same.

The estimated regression coefficients are presented in Table 4 . First, the first selected feature I i ( t ), which indicates whether all three control sliders have been explored via simple actions, has a positive regression coefficient on final outcome and a negative coefficient on duration. It means that, controlling the rest of the parameters, a student who has taken the VOTAT strategy tends to be more likely to give a correct answer and to complete in a shorter period of time. This confirms the strong effect of VOTAT strategy in solving the current task.

Table 4 . Estimated regression coefficients for a model for which the event history process contains the initial features based on polynomials of t and the top six features selected by cross validation.

Second, besides I i ( t ), there are two features related to taking simple actions, 1 { S i ( t )>0} and S i ( t )/ t , which are the indicator of taking at least one simple action and the frequency of taking simple actions. Both features have positive regression coefficients on the final outcome, implying larger values of both features lead to a higher success rate. In addition, 1 { S i ( t )>0} has a negative coefficient on duration and S i ( t )/ t has a positive one. Under this estimated model, the overall simple action effect on duration is b ^ 25 I i ( t ) + b ^ 26 1 { S i ( t ) > 0 } + b ^ 2 , 10 S i ( t ) / t , which is negative for most students. It implies that, overall, taking simple actions leads to a shorter predicted duration. However, once all three types of simple actions have been taken, a higher frequency of taking simple actions leads to a weaker but sill negative simple action effect on the duration.

Third, as discussed earlier, 1 { N i ( t )>0} tends to measure the student's speed of reading the instruction of the task and N i ( t )/ t can be regarded as a measure of students' speed of taking actions. According to the estimated regression coefficients, the data suggest that a student who reads and acts faster tends to complete the task in a shorter period of time with a lower accuracy. Similar results have been seen in the literature of response time analysis in educational psychology (e.g., Klein Entink et al., 2009 ; Fox and Marianti, 2016 ; Zhan et al., 2018 ), where speed of item response was found to negatively correlated with accuracy. In particular, Zhan et al. (2018) found a moderate negative correlation between students' general mathematics ability and speed under a psychometric model for PISA 2012 computer-based mathematics data.

Finally, 1 { R i ( t )>0} , the use of the RESET button, has positive regression coefficients on both final outcome and duration. It implies that the use of RESET button leads to a higher predicted success probability and a longer duration time, given the other features controlled. The connection between the use of the RESET button and the underlying cognitive process of complex problem solving, if it exists, still remains to be investigated.

5. Discussions

5.1. summary.

As an early step toward understanding individuals' complex problem-solving processes, we proposed an event history analysis method for the prediction of the duration and the final outcome of solving a complex problem based on process data. This approach is able to predict at any time t during an individual's problem-solving process, which may be useful in dynamic assessment/learning systems (e.g., in a game-based assessment system). An illustrative example is provided that is based on a CPS item from PISA 2012.

5.2. Inference, Prediction, and Interpretability

As articulated previously, this paper focuses on a prediction problem, rather than a statistical inference problem. Comparing with a prediction framework, statistical inference tends to draw stronger conclusions under stronger assumptions on the data generation mechanism. Unfortunately, due to the complexity of CPS process data, such assumptions are not only hardly satisfied, but also difficult to verify. On the other hand, a prediction framework requires less assumptions and thus is more suitable for exploratory analysis. As a price, the findings from the predictive framework are preliminary and can only be used to generate hypotheses for future studies.

It may be useful to provide uncertainty measures for the prediction performance and for the parameter estimates, where the former indicates the replicability of the prediction performance and the later reflects the stability of the prediction model. In particular, patterns from a prediction model with low replicability and low stability should not be overly interpreted. Such uncertainty measures may be obtained from cross validation and bootstrapping (see Chapter 7, Friedman et al., 2001 ).

It is also worth distinguishing prediction methods based on a simple model like the one proposed above and those based on black-box machine learning algorithms (e.g., random forest). Decisions based on black-box algorithms can be very difficult to understood by human and thus do not provide us insights about the data, even though they may have a high prediction accuracy. On the other hand, a simple model can be regarded as a data dimension reduction tool that extracts interpretable information from data, which may facilitate our understanding of complex problem solving.

5.3. Extending the Current Model

The proposed model can be extended along multiple directions. First, as discussed earlier, we may extend the model by allowing the regression coefficients b jk to be time-dependent. In that case, nonparametric estimation methods (e.g., splines) need to be developed for parameter estimation. In fact, the idea of time-varying coefficients has been intensively investigated in the event history analysis literature (e.g., Fan et al., 1997 ). This extension will be useful if the effects of the features in H i ( t ) change substantially over time.

Second, when the dimension p of H i ( t ) is high, better interpretability and higher prediction power may be achieved by using Lasso-type sparse estimators (see e.g., Chapter 3 Friedman et al., 2001 ). These estimators perform simultaneous feature selection and regularization in order to enhance the prediction accuracy and interpretability.

Finally, outliers are likely to occur in the data due to the abnormal behavioral patterns of a small proportion of people. A better treatment of outliers will lead to better prediction performance. Thus, a more robust objective function will be developed for parameter estimation, by borrowing ideas from the literature of robust statistics (see e.g., Huber and Ronchetti, 2009 ).

5.4. Multiple-Task Analysis

The current analysis focuses on analyzing data from a single task. To study individuals' CPS ability, it may be of more interest to analyze multiple CPS tasks simultaneously and to investigate how an individual's process data from one or multiple tasks predict his/her performance on the other tasks. Generally speaking, one's CPS ability may be better measured by the information in the process data that is generalizable across a representative set of CPS tasks than only his/her final outcomes on these tasks. In this sense, this cross-task prediction problem is closely related to the measurement of CPS ability. This problem is also worth future investigation.

Author Contributions

All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.

This research was funded by NAEd/Spencer postdoctoral fellowship, NSF grant DMS-1712657, NSF grant SES-1826540, NSF grant IIS-1633360, and NIH grant R01GM047845.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

1. ^ The item can be found on the OECD website ( http://www.oecd.org/pisa/test-2012/testquestions/question3/ )

2. ^ The log file data and code book for the CC item can be found online: http://www.oecd.org/pisa/pisaproducts/database-cbapisa2012.htm .

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Keywords: process data, complex problem solving, PISA data, response time, event history analysis

Citation: Chen Y, Li X, Liu J and Ying Z (2019) Statistical Analysis of Complex Problem-Solving Process Data: An Event History Analysis Approach. Front. Psychol . 10:486. doi: 10.3389/fpsyg.2019.00486

Received: 31 August 2018; Accepted: 19 February 2019; Published: 18 March 2019.

Reviewed by:

Copyright © 2019 Chen, Li, Liu and Ying. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Yunxiao Chen, [email protected]

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

Statistical Problem Solving (SPS) 870274

In today's global market, quality improvement has become an essential element of remaining competitive. Given a stable manufacturing process, there are two competing strategies for improving it. The first, a conventional approach, relies on a “one factor at a time” strategy, usually requires added costs, and is often limited in its success. The second approach relies on methods grouped under the name “Statistical Problem Solving” (SPS) and simultaneously exploits statistical science, teamwork, existing process knowledge, and execution strategies. Problems are solved and processes improved by reducing statistical variation at virtually zero cost. This paper reviews the conventional problem-solving approach with some of its shortcomings, then systematically presents the SPS strategy.

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Root Cause Problem Solving - Methods and Tools

Statistical Methods Needed to Achieve New Quality Levels and to Sustain the Improvement

How to Solve Statistics Problems Accurately

Several students are struggling with the problem of mathematics numeric problems. A study shows that almost 30% of students are unable to solve quantitative problems. 

Therefore, in this blog, you will find effective solutions for how to solve statistics problems. Here you will find various advanced quantitative data analysis courses. 

Because of the various uses of these statistics problems in everyone’s daily lives, students still lack solving these kinds of problems. That is why it becomes necessary to understand the methods to tackle the problem of statistics. 

So, let’s check all the necessary techniques to solve quantitative data problems.

What is statistics? 

Table of Contents

It is one of the branches of mathematics statistics that involves collecting, examining, presenting, and representing data. 

Once the information is accumulated, reviewed, and described as charts, one may see for drifts and attempt to execute forecasts depending on certain factors.

Now, you have understood the meaning of statistics. So, it is the right time to get familiar with the steps used for how to solve statistics problems. 

Here, you will find out these techniques with a suitable example. This will help you to know how these techniques are implemented to solve quantitative statistics problems. 

But before moving to the strategies, let’s check whether you have effective knowledge of statistics or not. This will also help you to check whether your concepts about the statistics problem are cleared or not. 

Once you know that you have an effective understanding of statistics, you can easily solve the statistics problems.

Take a test of your statistics knowledge !!!

Give the answers to questions mentioned below:

• How long do seniors spend clipping their nails?
• Not statistical
• Statistical
• None of both
• How many days are in Feb?
• Did Rose watch TV last night?
• How many cyberspace searches do citizens have at a Retirement each day?
• How long is the rapunzel’s hair?
• The average height of a giraffe?
• How many nails does Alan have in his hand?
• How old is my favourite teacher?
• What does my favorite basketball team weigh?
• Does Morris have a university degree?

Now, you have tested your knowledge so we can move to the strategies to solve a statistical problem.

Strategies for how to solve statistics problems

Let’s take a statistical problem and understand the strategies to solve it. The below strategies are based on the random sample problem and solve it sequentially.

#1: Relax and check out the given statistics problem

When students assign the statistics problems, you have noticed that they get panicked. Due to panic, there are higher chances of making errors while solving statistics distributions. 

This might be because students think that they can solve these queries, leading to low confidence. That is why it becomes necessary to calm yourself before you start to solve any statistics problem. 

Here is an example that helps you to understand the statistics problem easily.  

Almost 17 boys were diagnosed with a specific disease that leads to weight change. 

Here the data after family therapy was as follows:

11,11, 6, 9, 14, -3, 0, 7, 22, -5 , -4, 13, 13, 9, 4 , 6, 11

#2: Analyze the statistics problem

Once you assign the statistics problem, now analyze the query to solve it accurately. 

Check what does it ask you to perform in the problem? It would help if one obtained the upper confidence limit that can utilize the mean: the degrees of freedom and the t-value.

Here is the question: what is the meaning of the degrees of freedom to a t-test?

Take a sample question: If there are n number of observations. It would help if you estimated the mean value. This will leave the n-1 degree of freedom that is utilized for estimated variability.

For the above problem, we can estimate the average along with the sample value 17-1 that is equal to 16.

To recognize the difficulty, study the numbers one can DO have.

• One should have a lower confidence limit.
• Get all of the specific scores.
• You need to understand the number of scores (17).

Consider the things about what one can DO remember (or may view within a textbook).

• The mean score of the number is the addition of the scores divided with the total score number.
• To get the lower confidence limit, one needs to do minus (t * standard error).
• An UPPER confidence limit is the collected average + (t * standard error).

#3: Choose the strategy for how to solve statistics problems

There are several methods to get the upper confidence limit; besides this, all this includes the calculating value (t*standard error) to get the mean. There are the easiest approach is

• Determine what the mean does.
• Check the difference in the mean and the limit of lower confidence.
• Sum the number to the mean.

These are steps where most people get puzzled. This might be because of the three main reasons. 

• The first one is that students are stressed out because of indulging in various academic studies. 
• Secondly, learners do not have enough time to check the statistics problems and recognize what to do first. 
• Thirdly, they do not rest a single minute and study the right approach. 

We think that several students do not pay sufficient time on the initial three levels before skipping to the fourth number.

#4: Perform it right now

Take out a strategy.

• The mean will be 7.29.
• 7.29 -3.6 = 3.69
• Sum 3.69 to 7.29 to get 10.98

This is the correct answer.

#5: Verify the to know how to solve statistics problems

Do a certainty verification. The mean must be 7.29. If it does not lay in the category of lower and upper confidence limits, then there would be something wrong.

Check again tomorrow to get the verification of the number. These steps would be implemented to all statistics problems (and a math query – might be a puzzle in life.)

Let’s understand the above steps by solving a statistical problem!!

Problem: In a state, there are 52% of voters Democrats, and almost 48% are republicans. In another state, 47% of voters are Democrats, and 53% are Republicans. If the sample takes 100 voters, then what probability represents the maximum percentage of Democrats in another state.

Solution: 

P1 = Republican voters proportion in the first state, 

P2 = Republican voters proportion in another state, 

p1 = Sample Republican voters proportion in the first state, 

p2 = Sample Republican voters proportion in another state, 

n1 = Number of voters in the first state, 

n2 = Number of voters in another state, 

Now, let’s solve it in four steps:

• Remember that the sample size must be bigger to model difference for a normal population. Therefore, P1*n1 = 0.52*100 =52, (1-P1)*n1 = 0.48 *100 = 48.

On the other hand, P2*n2 = 0.47*100 =47, (1-P2)*n2 = 0.53*100 = 53, which is greater than 10. So we can say that sample size is much larger.

• Calculate the mean of the sample proportions difference: E(p1 – p2) => P1 – P2 = 0.52 – 0.47 => 0.05.
• Calculate the difference of standard deviation.

σd = sqrt{[ (1 – P2)*P2 / n2 ] + [ (1 – P1)*P1 / n1 ] }

σd = sqrt{[(0.53)*(0.47) / 100 ] + [ (0.48)*(0.52) / 100 ] }

σd = sqrt ( 0.002491 + 0.002496 ) = sqrt(0.004987) = 0.0706

• Calculate the probability. The given problem needs to calculate the probability, which is p1 < p2. 

This is similar to determining the probability, which is (p1 – p2) < 0. To calculate the probability, you must transform the variable (p1 – p2) in the z-score. The transformation will be:

z (base (p1 – p2)) = (x – μ (base (p1 – p2) ) / σd = (0 – 0.05)/0.0706 => -0.7082

• With the help of the Normal Distribution calculator of Stat Trek’s, you can calculate that the Z-scores probability that is being -0.7082 is 0.24.

That is why the probability shows a greater % of Republican voters within another/second state as compared to the first state, and it is 0.24.

Conclusion 

To sum up this post, we can say that we have defined the possible strategies about how to solve statistics problems. Moreover, we have mentioned the procedure for solving the statistics queries that help students solve mathematics in their daily lives. 

Besides this, we have provided solutions with detailed examples. So that students can easily understand the techniques and implement them to solve statistics terms. 

Analyzing these examples can allow the students to know the sequence of solving a statistics question. Follow the steps mentioned above to get the desired result of the problems and verify them accordingly. Learn and practice the initial rule to solve each problem of quantitative analysis effectively. Get the best statistics homework help .

Frequently Asked Questions

What are the four steps to organize a statistical problem.

The Four-Step to organize the statistical problem:

STATE: The real-world or a practical problem. FORMULATE: Which is the best formula to solve the problem? SOLVE: Make relevant charts and graphs and practice the required calculations. CONCLUDE: Take the summary to set the real-world problems.

What is a good statistical question?

A statistical problem can be solved by gathering useful data and checking where the variability is in the given data. For instance, there is variability in the collected data to solve the problem, “What does the animal weigh at Fancy Farm?” but not to solve, “What is the colour of Ana’s hat?”

What is the most important thing in statistics?

The three basic components of statistics are determination, measurement, and modification. Randomness is considered one way to supply development, and it is another way to model variations.

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How to Find the Best Online Statistics Homework Help

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Wavefunction matching for solving quantum many-body problems

Strongly interacting systems play an important role in quantum physics and quantum chemistry. Stochastic methods such as Monte Carlo simulations are a proven method for investigating such systems. However, these methods reach their limits when so-called sign oscillations occur. This problem has now been solved by an international team of researchers from Germany, Turkey, the USA, China, South Korea and France using the new method of wavefunction matching. As an example, the masses and radii of all nuclei up to mass number 50 were calculated using this method. The results agree with the measurements, the researchers now report in the journal " Nature ."

All matter on Earth consists of tiny particles known as atoms. Each atom contains even smaller particles: protons, neutrons and electrons. Each of these particles follows the rules of quantum mechanics. Quantum mechanics forms the basis of quantum many-body theory, which describes systems with many particles, such as atomic nuclei.

One class of methods used by nuclear physicists to study atomic nuclei is the ab initio approach. It describes complex systems by starting from a description of their elementary components and their interactions. In the case of nuclear physics, the elementary components are protons and neutrons. Some key questions that ab initio calculations can help answer are the binding energies and properties of atomic nuclei and the link between nuclear structure and the underlying interactions between protons and neutrons.

However, these ab initio methods have difficulties in performing reliable calculations for systems with complex interactions. One of these methods is quantum Monte Carlo simulations. Here, quantities are calculated using random or stochastic processes. Although quantum Monte Carlo simulations can be efficient and powerful, they have a significant weakness: the sign problem. It arises in processes with positive and negative weights, which cancel each other. This cancellation leads to inaccurate final predictions.

A new approach, known as wavefunction matching, is intended to help solve such calculation problems for ab initio methods. "This problem is solved by the new method of wavefunction matching by mapping the complicated problem in a first approximation to a simple model system that does not have such sign oscillations and then treating the differences in perturbation theory," says Prof. Ulf-G. Meißner from the Helmholtz Institute for Radiation and Nuclear Physics at the University of Bonn and from the Institute of Nuclear Physics and the Center for Advanced Simulation and Analytics at Forschungszentrum Jülich. "As an example, the masses and radii of all nuclei up to mass number 50 were calculated -- and the results agree with the measurements," reports Meißner, who is also a member of the Transdisciplinary Research Areas "Modeling" and "Matter" at the University of Bonn.

"In quantum many-body theory, we are often faced with the situation that we can perform calculations using a simple approximate interaction, but realistic high-fidelity interactions cause severe computational problems," says Dean Lee, Professor of Physics from the Facility for Rare Istope Beams and Department of Physics and Astronomy (FRIB) at Michigan State University and head of the Department of Theoretical Nuclear Sciences.

Wavefunction matching solves this problem by removing the short-distance part of the high-fidelity interaction and replacing it with the short-distance part of an easily calculable interaction. This transformation is done in a way that preserves all the important properties of the original realistic interaction. Since the new wavefunctions are similar to those of the easily computable interaction, the researchers can now perform calculations with the easily computable interaction and apply a standard procedure for handling small corrections -- called perturbation theory.

The research team applied this new method to lattice quantum Monte Carlo simulations for light nuclei, medium-mass nuclei, neutron matter and nuclear matter. Using precise ab initio calculations, the results closely matched real-world data on nuclear properties such as size, structure and binding energy. Calculations that were once impossible due to the sign problem can now be performed with wavefunction matching.

While the research team focused exclusively on quantum Monte Carlo simulations, wavefunction matching should be useful for many different ab initio approaches. "This method can be used in both classical computing and quantum computing, for example to better predict the properties of so-called topological materials, which are important for quantum computing," says Meißner.

The first author is Prof. Dr. Serdar Elhatisari, who worked for two years as a Fellow in Prof. Meißner's ERC Advanced Grant EXOTIC. According to Meißner, a large part of the work was carried out during this time. Part of the computing time on supercomputers at Forschungszentrum Jülich was provided by the IAS-4 institute, which Meißner heads.

• Quantum Computers
• Computers and Internet
• Computer Modeling
• Spintronics Research
• Mathematics
• Quantum mechanics
• Quantum entanglement
• Introduction to quantum mechanics
• Computer simulation
• Quantum computer
• Quantum dot
• Quantum tunnelling
• Security engineering

Story Source:

Materials provided by University of Bonn . Note: Content may be edited for style and length.

Journal Reference :

• Serdar Elhatisari, Lukas Bovermann, Yuan-Zhuo Ma, Evgeny Epelbaum, Dillon Frame, Fabian Hildenbrand, Myungkuk Kim, Youngman Kim, Hermann Krebs, Timo A. Lähde, Dean Lee, Ning Li, Bing-Nan Lu, Ulf-G. Meißner, Gautam Rupak, Shihang Shen, Young-Ho Song, Gianluca Stellin. Wavefunction matching for solving quantum many-body problems . Nature , 2024; DOI: 10.1038/s41586-024-07422-z

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