Essentials Of Statistics For Business & Economics
9th Edition
ISBN: 9780357045435
Author: David R. Anderson, Dennis J. Sweeney, Thomas A. Williams, Jeffrey D. Camm, James J. Cochran
Publisher: South-Western College Pub
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Chapter 6, Problem 53SE
Do you dislike waiting in line? Supermarket chain Kroger has used computer simulation and information technology to reduce the average waiting time for customers at 2300 stores. Using a new system called QueVision, which allows Kroger to better predict when shoppers will be checking out, the company was able to decrease average customer waiting time to just 26 seconds (InformationWeek website and The Wall Street Journal website, January 5, 2015).
- a. Assume that Kroger waiting times are exponentially distributed. Show the
probability densityfunction of waiting time at Kroger. - b. What is the probability that a customer will have to wait between 15 and 30 seconds?
- c. What is the probability that a customer will have to wait more than 2 minutes?
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3. Bayesian Inference – Updating Beliefs
A medical test for a rare disease has the following characteristics:
Sensitivity (true positive rate): 99%
Specificity (true negative rate): 98%
The disease occurs in 0.5% of the population.
A patient receives a positive test result.
Questions:
a) Define the relevant events and use Bayes’ Theorem to compute the probability that the patient actually has the disease.b) Explain why the result might seem counterintuitive, despite the high sensitivity and specificity.c) Discuss how prior probabilities influence posterior beliefs in Bayesian inference.d) Suppose a second, independent test with the same accuracy is conducted and is also positive. Update the probability that the patient has the disease.
4. Linear Regression - Model Assumptions and Interpretation
A real estate analyst is studying how house prices (Y) are related to house size in square feet (X). A simple
linear regression model is proposed:
The analyst fits the model and obtains:
•
Ŷ50,000+150X
YBoB₁X + €
•
R² = 0.76
• Residuals show a fan-shaped pattern when plotted against fitted values.
Questions:
a) Interpret the slope coefficient in context.
b) Explain what the R² value tells us about the model's performance.
c) Based on the residual pattern, what regression assumption is likely violated? What might be the
consequence?
d) Suggest at least two remedies to improve the model, based on the residual analysis.
Chapter 6 Solutions
Essentials Of Statistics For Business & Economics
Ch. 6.1 - The random variable x is known to be uniformly...Ch. 6.1 - The random variable x is known to be uniformly...Ch. 6.1 - Cincinnati to Tampa Flight Time. Delta Airlines...Ch. 6.1 - Excel RAND Function. Most computer languages...Ch. 6.1 - Tesla Battery Recharge Time. The electric-vehicle...Ch. 6.1 - A Gallup Daily Tracking Survey found that the mean...Ch. 6.1 - 7. Suppose we are interested in bidding on a piece...Ch. 6.2 - Using Figure 6.6 as a guide, sketch a normal curve...Ch. 6.2 - A random variable is normally distributed with a...Ch. 6.2 - Draw a graph for the standard normal distribution....
Ch. 6.2 - Given that z is a standard normal random variable,...Ch. 6.2 - Given that z is a standard normal random variable,...Ch. 6.2 - 13. Given that z is a standard normal random...Ch. 6.2 - Given that z is a standard normal random variable,...Ch. 6.2 - Given that z is a standard normal random variable,...Ch. 6.2 - Given that z is a standard normal random variable,...Ch. 6.2 - Height of Dutch Men. Males in the Netherlands are...Ch. 6.2 - Large-Cap Domestic Stock Fund. The average return...Ch. 6.2 - Automobile Repair Costs. Automobile repair costs...Ch. 6.2 - Gasoline Prices. Suppose that the average price...Ch. 6.2 - Mensa Membership. A person must score in the upper...Ch. 6.2 - Television Viewing. Suppose that the mean daily...Ch. 6.2 - Time to Complete Final Exam. The time needed to...Ch. 6.2 - Labor Day Travel Costs. The American Automobile...Ch. 6.2 - Household Income in Maryland. According to Money...Ch. 6.3 - A binomial probability distribution has p=.20 and...Ch. 6.3 - Assume a binomial probability distribution has p =...Ch. 6.3 - Adults Who Smoke. Although studies continue to...Ch. 6.3 - Americans Who Believe Global Warming Is Occurring....Ch. 6.3 - Playing Video Games. Suppose that of those...Ch. 6.3 - Visitors to Rocky Mountain National Park. Rocky...Ch. 6.4 - Consider the following exponential probability...Ch. 6.4 - 33. Consider the following exponential probability...Ch. 6.4 - 34. Battery life between charges for the Motorola...Ch. 6.4 - 35. The time between arrivals of vehicles at a...Ch. 6.4 - 36. Comcast Corporation is the largest cable...Ch. 6.4 - 37. Wendy’s restaurant has been recognized for...Ch. 6.4 - 38. The Boston Fire Department receives 911 calls...Ch. 6 - 39. A business executive, transferred from Chicago...Ch. 6 - NCAA Scholarships. The NCAA estimates that the...Ch. 6 - Production Defects. Motorola used the normal...Ch. 6 - Bringing Items to a Pawnshop. One indicator of the...Ch. 6 - Amazon Alexa App Downloads. Alexa is the popular...Ch. 6 - Service Contract Offer. Ward Doering Auto Sales is...Ch. 6 - Wedding Costs. The XO Group Inc. conducted a 2015...Ch. 6 - College Admissions Test Scores. Assume that the...Ch. 6 - College Graduates Starting Salaries. According to...Ch. 6 - 48. A machine fills containers with a particular...Ch. 6 - Multiple-Choice Exam. Consider a multiple-choice...Ch. 6 - Playing Blackjack. A blackjack player at a Las...Ch. 6 - Mean Time Between Failures. The mean time between...Ch. 6 - The website for the Bed and Breakfast Inns of...Ch. 6 - Do you dislike waiting in line? Supermarket chain...Ch. 6 - Prob. 54SE
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