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Statistics Data Analysis And Decision Modeling 5th Edition James R. Evans - Solutions
What is a confidence interval? How do you properly interpret the level of confidence, 1 – (?
Summarize the different types of confidence intervals that one may construct, and provide a practical application for each.
Discuss how confidence intervals can help in making decisions. Provide some examples different from those in the chapter.
Under what circumstances can confidence intervals be applied to time‐series data?
Explain how a confidence interval changes with changes in the level of confidence and sample size.
What is a sampling plan and what elements should be included in one?
What is a prediction interval and how does it differ from a confidence interval?
How does a frame differ from a target population?
Describe the difference between subjective and probabilistic sampling methods. What are the advantages and disadvantages of each?
Explain how the following sampling approaches work:a. Simple random samplingb. Systematic samplingc. Stratified samplingd. Cluster samplinge. Sampling from a continuous process
What is the difference between nonsampling error and sampling error? Why might each type of error occur?
Define a random number. How is it different from a random variate?
Explain the sampling distribution of the mean. What properties does it have?
What is the standard error of the mean? How does it relate to the standard deviation of the population from which a sample is taken?
Your college or university wishes to obtain reliable information about student perceptions of administrative communication. Describe how to implement sampling plans for this situation using simple random sampling, stratified sampling, and cluster sampling.
Using the data in the worksheet Consumer Transportation Survey, develop 95% and 99% confidence intervals for the following:a. The mean hours per week that individuals spend in their vehiclesb. The average number of miles driven per weekc. The proportion of individuals who are satisfied with their
The Excel file Restaurant Sales provides sample information on lunch, dinner, and delivery sales for a local Italian restaurant. Develop 95% confidence intervals for the mean of each of these variables, as well as for weekday and weekend sales. What conclusions can you reach?
The Excel file Infant Mortality provides data on infant mortality rate (deaths per 1,000 births), female literacy (percentage who read), and population density (people per square kilometer) for 85 countries. Develop a 90% confidence interval for infant mortality.
A manufacturer conducted a survey among 400 randomly selected target market households in the test market for its new disposable diapers. The objective of the survey was to determine the market share for its new brand. If the sample point estimate for market share is 18%, develop a 95% confidence
If, based on a sample size of 600, a political candidate finds that 318 people would vote for him in a two person race, what is the 95% confidence interval for his expected proportion of the vote? Would he be confident of winning based on this poll?
If, based on a sample size of 200, a political candidate found that 125 people would vote for her in a two person race, what is the 95% confidence interval for her expected proportion of the vote? Would she be confident of winning based on this poll?
The Excel file Blood Pressure shows diastolic blood pressure readings before and after a new medication. Find 95% confidence intervals for the variance for each of these groups. Based on these confidence intervals, would you conclude that the medication has kept the reading more stable?
Using data in the Excel file Colleges and Universities, find 95% confidence intervals for the standard deviation of the median SAT for each of the two groups: liberal arts colleges and research universities. Based on these confidence intervals, does there appear to be a difference in the variation
An auditor of a small business has sampled 50 of 750 accounts. The sample mean total receivables is $525, and the sample standard deviation is $80. Find a 95% confidence interval for the total amount of receivables.
The Excel file New Account Processing provides data for a sample of employees in a company. Assume that the company has 125 people in total assigned to new account processing. Find a 95% confidence interval for the total sales of the population of account representatives.
Trade associations such as the United Dairy Farmers Association frequently conduct surveys to identify characteristics of their membership. If this organization conducted a survey to estimate the annual per‐capita consumption of milk and wanted to be 95% confident that the estimate was no more
If a manufacturer conducted a survey among randomly selected target market households and wanted to be 95% confident that the difference between the sample estimate and the actual market share for its new product was no more than (3 %, what sample size would be needed?
The Excel file Baseball Attendance shows the attendance in thousands at San Francisco Giants’ baseball games for the 10 years before the Oakland A’s moved to the Bay Area in 1968, as well as the combined attendance for both teams for the next 11 years.a. Do the data appear to be stationary?b.
The state of Ohio Department of Education has a mandated ninth‐grade proficiency test that covers writing, reading, mathematics, citizenship (social studies), and science. The Excel file Ohio Education Performance provides data on success rates (defined as the percentage of students passing) in
Using the data in the worksheet Consumer Transportation Survey, develop 95% and 99% prediction intervals for the following: a. The hours per week that an individual will spend in his or her vehicle b. The number of miles driven per week Compare these to the confidence intervals developed in
The Excel file Restaurant Sales provides sample information on lunch, dinner, and delivery sales for a local Italian restaurant. Develop 95% prediction intervals for the dollar sales of each of these variables for next Saturday.
For the Excel file Credit Approval Decisions, find 95% confidence and prediction intervals for the credit scores and revolving balance of homeowners and nonhomeowners. How do they compare?
A study of nonfatal occupational injuries in the United States found that about 31% of all injuries in the service sector involved the back. The National Institute for Occupational Safety and Health (NIOSH) recommended conducting a comprehensive ergonomics assessment of jobs and workstations. In
A marketing study found that the mean spending in 15 categories of consumer items for 297 respondents in the 18–34 age group was $71.86 with a standard deviation of $70.90. For 736 respondents in the 35+ age group, the mean and standard deviations were $61.53 and $45.29, respectively. Develop 95%
The Excel file Mortgage Rates contains time‐series data on rates of three different mortgage instruments. Assuming that the data are stationary, construct a 95% confidence interval for the mean difference between the 30‐year and 15‐year fixed rate mortgage rates. Based on this confidence
The weekly demand of a slow‐moving product has the probability mass function: Demand, x Probability, f(x)0 ……………………………..0.11 ……………………………..0.32 ……………………………..0.43 ……………………………..0.24 or more
The Excel file Student Grades contains data on midterm and final exam grades in one section of a large statistics course. Construct a 95% confidence interval for the mean difference in grades between the midterm and final exams.
Suppose that we conduct an experiment in which samples of size n are generated from a normal distribution having a known standard deviation σ. If we compute the range of each sample, we can estimate the distribution of the statistic R/σ. The expected value of this statistic is a factor that
In determining automobile mileage ratings, it was found that the mpg in the city for a certain model is normally distributed, with a mean of 24 mpg and a standard deviation of 1.0 mpg. Suppose that the car manufacturer samples 9 cars from its assembly line and tests them for mileage ratings.a. What
A popular soft drink is sold in 2‐liter (2,000 mL) bottles. Because of variation in the filling process, bottles have a mean of 2,000 mL and a standard deviation of 20, normally distributed.a. If the manufacturer samples 100 bottles, what is the probability that the mean is less than 1,950 mL?b.
Using the data in the Excel file Accounting Professionals, find and interpret 95% confidence intervals for the following:a. Mean years of serviceb. Proportion of employees who have a graduate degree
Using the data in the Excel file MBA Student Survey, find 95% confidence intervals for the mean number of nights out per week and mean number of study hours per week by gender. Based on the confidence intervals, would you conclude that there is a difference in social and study habits between males
Explain the notion of hypothesis testing. What is the general process that one should follow in conducting a hypothesis test?
Explain the peculiar nuances associated with the Excel tools for two‐sample t ‐tests. What issues must you consider to use the tests and interpret the results properly?
What is the difference between paired and independent samples?
Explain the relationship between confidence intervals and hypothesis testing.
Explain how to interpret the Excel results for a hypothesis test for equality of variances.
What is analysis of variance? What hypothesis does it test? Provide some practical examples.
What are the key assumptions of ANOVA? What should be done if these are seriously violated?
Explain the purpose of the chi‐square test for independence. Provide some practical examples where this test might be used in business.
Explain the difference between the null and alternative hypothesis. Which one can be proven in a statistical sense?
What are the differences between one‐ and two‐sample hypothesis tests? Describe the correct mathematical form for specifying the null and alternative hypotheses for both types of tests.
Explain Type I and Type II errors. Which one is controllable by the experimenter?
Explain how the rejection region is determined for a hypothesis test. How does it differ between one‐ and two‐tailed tests?
What is a p‐value? How is it used to reach a conclusion about a hypothesis test?
How are Type II errors influenced by the true (unknown) population mean and sample size used in a hypothesis test?
A producer of computer‐aided design software for the aerospace industry receives numerous calls for technical support. Tracking software is used to monitor response and resolution times. In addition, the company surveys customers who request support using the following scale: 0-Did not exceed
Jim Aspenwall, a NASCAR enthusiast, has compiled some key statistics for NASCAR Winston Cup racing tracks across the United States. These tracks range in shape, length, and amount of banking on the turns and straightaways (see the Excel file NASCAR Track Data). Test the hypothesis that there is no
The Excel file Blood Pressure shows the monthly blood pressure (diastolic) readings for a patient before and after medication.a. Test the hypothesis that the variances of monthly blood pressure readings before and after medication are the same.b. Conduct an appropriate hypothesis test to determine
An engineer measured the surface finish of 35 parts produced on a lathe, noting the revolutions per minute of the spindle and the type of tool used (see the Excel file Surface Finish). Use ANOVA to test the hypothesis that the mean surface finish is the same for each tool. If the null hypothesis is
A mental health agency measured the self‐esteem score for randomly selected individuals with disabilities who were involved in some work activity within the past year. The Excel file Self Esteem provides the data, including the individuals’ marital status, length of work, type of support
For the data in the Excel file New Account Processing, perform chi‐square tests for independence to determine if certification is independent of gender, and if certification is independent of having prior industry background.
In the Excel file New Account Processing, test the null hypothesis that the variance in the Close Ratio for the sample of employees is at most 1.5%.
In the Excel file Gasoline Prices, determine if there is evidence to conclude that the variance of weekly prices during 2009 is less than 10%.
The Excel file HATCO1 consists of data related to predicting the level of business obtained from a survey of purchasing managers of customers of an industrial supplier, HATCO. The variables are as follows:• Delivery Speed—amount of time it takes to deliver the product once an order is
Provide some practical examples from your work experience where regression models might be used.
Explain the assumptions of linear regression. How can you determine if each of these assumptions holds?
What are partial regression coefficients, and what information do they provide?
Explain how adjusted R2 is used in evaluating the fit of multiple regression models.
What is the difference in the hypotheses tested in single and multiple regression using the Significance F ‐statistic?
What is multicollinearity, and how is it measured? What problems can it cause in regression results?
Describe the systematic process for building a good regression model.
Describe the differences and advantages/disadvantages of using stepwise and best‐subsets approaches in building regression models.
How should you balance technical criteria and practical judgment in building regression models?
Explain how to include categorical variables in regression models.
What is interaction, and why is it important to test for it?
Explain the difference between simple and multiple linear regression.
What is a curvilinear regression model? How do you know when to use one?
What is least‐squares regression? Describe how least squares regression defines the best‐fitting regression line.
How can regression analysis be applied to understand risk associated with stocks and mutual funds?
Explain what the coefficient of determination, R2, measures. How is it related to the sample correlation co-efficient?
What is the standard error of the estimate? What information does it provide?
Explain what information Excel provides to interpret regression analysis.
How are standard residuals calculated, and how can they help identify outliers?
A deep‐foundation engineering contractor has bid on a foundation system for a new world headquarters building for a Fortune 500 company. A part of the project consists of installing 311 auger cast piles. The contractor was given bid information for cost‐estimating purposes, which consisted of
The Excel file Concert Sales provides data on sales dollars and the number of radio and TV and newspaper ads promoting the concerts for a group of cities. Develop simple linear regression models for predicting sales as a function of the number of each type of ad. Compare these results to a multiple
Using the data in the Excel file Home Market Value, develop a multiple linear regression model for estimating the market value as a function of both the age and size of the house. Find a 95% confidence interval for the mean market value for houses that are 30 years old and have 1,800 square feet
The Excel file Infant Mortality provides data on infant mortality rate (deaths per 1,000 births), female literacy (percent who read), and population density (people per square kilometer) for 85 countries. Develop the best multiple regression model for the relationship between mortality, population
The Excel file Cereal Data provides a variety of nutritional information about 67 cereals and their shelf location in a supermarket. Use regression analysis to find the best model that explains the relationship between calories and the other variables. Investigate the model assumptions and clearly
The Excel file Salary Data provides information on current salary, beginning salary, previous experience (in months) when hired, and total years of education for a sample of 100 employees in a firm.a. Develop a multiple regression model for predicting current salary as a function of the other
The Excel file Credit Approval Decisions provides information on credit history for a sample of banking customers. Use regression analysis to identify the best model for predicting the credit score as a function of the other numerical variables. For the model you select, conduct further analysis to
Using the data in the Excel file Freshman College Data, identify the best regression model for predicting the first year retention rate. For the model you select, conduct further analysis to check for significance of the independent variables and for multicollinearity.
The Excel file Major League Baseball provides data on the 2010 season.a. Construct and examine the correlation matrix. Is multicollinearity a potential problem? Find the variance inflation factors to check your intuition.b. Suggest an appropriate set of independent variables that predict the number
The Excel file Golfing Statistics provides data for a portion of the 2010 professional season for the top 25 golfers.a. Find the best multiple regression model for predicting earnings/event as a function of the remaining variables.b. Find the best multiple regression model for predicting average
Using the data in the Excel file Student Grades, construct a scatter chart for midterm versus final exam grades and add a linear trendline. What is the regression model and R2 ? If a student scores 85 on the midterm, what would you estimate her grade on the final exam to be?
Apply stepwise regression using each selection rule and p ‐value criterion to find a good model for predicting the number of points scored per game by football teams using the data in the Excel file National Football League. Compare your results.
Apply stepwise regression using the each selection rule and t ‐value criterion to find the best model for predicting the number of wins in the Major League Baseball data. Compare your results. How do the stepwise models compare with your answer to problem 18(c)?
Apply stepwise regression using each selection rule and p‐value criterion to find the best models for predicting earnings/event and average score in the Golfing Statistics data. How do the stepwise models compare with your answer to problem 19?
Apply best‐subsets regression to find the best model for explaining the relationship between calories and the other variables in the Excel file Cereal Data. Use the regression tool to run your selected model, and explain all statistical results.
Apply best‐subsets regression to find the best model for explaining the relationship between calories and the other variables in the Excel file Salary Data. Use the regression tool to run your selected model, and explain all statistical results.
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