Consider again the data in Exercise 29 about the gas mileage and weights of cars. a) Create a 95% confidence interval for the slope of the regression line. b) Explain in this context what your confidence interval means.
> Real estate agents want to set correctly the price of a house that’s about to go on the real estate market. They must choose a price that strikes a balance between one that is so high that the house takes too long to sell and one that’s so low that not e
> Find the critical value t* for: a) a 95% confidence interval based on 24 df. b) a 95% confidence interval based on 99 df.
> A leading manufacturer of exercise equipment wanted to collect data on the effectiveness of their equipment. An August 2001 article in the journal Medicine and Science in Sports and Exercise compared how long it would take men and women to burn 200 calor
> A small company, on hearing about the employee athlete program (see Exercise 75) at the large company down the street, decides to try it as well. To measure the difference in productivity, they measure the average number of keystrokes per hour of 23 empl
> An ergonomics consultant is engaged by a large consumer products company to see what they can do to increase productivity. The consultant recommends an “employee athlete” program, encouraging every employee to devote 5
> Exercises 70 and 72 give summaries and displays for two potential sites for a wind turbine. Test an appropriate hypothesis to see if there is evidence that either of these sites has a higher average wind speed. Exercises 70: Alternative sources of energ
> Exercises 69 and 71 give summaries and displays for car insurance premiums quoted by a local agent and an online company. Test an appropriate hypothesis to see if there is evidence that drivers might save money by switching to the online company. Exerc
> In Exercise 70, we saw summary statistics for wind speeds at two sites near each other, both being considered as locations for an electricity-generating wind turbine. The data, recorded every 6 hours for a year, showed each of the sites had a mean wind s
> In Exercise 69, we saw summary statistics for 10 drivers’ car insurance premiums quoted by a local agent and an online company. Here are displays for each company’s quotes and for the difference (Local â€
> Alternative sources of energy are of increasing interest throughout the energy industry. Wind energy has great potential. But appropriate sites must be found for the turbines. To select the site for an electricitygenerating wind turbine, wind speeds were
> After seeing countless commercials claiming one can get cheaper car insurance from an online company, a local insurance agent was concerned that he might lose some customers. To investigate, he randomly selected profiles (type of car, coverage, driving r
> It has long been a dream of farmers to summon rain when it is needed for their crops. Crop losses to drought have significant economic impact. One possibility is cloud seeding, in which chemicals are dropped into clouds in an attempt to induce rain. Simp
> For the data in Exercise 8: a) How many degrees of freedom does the t-statistic have? b) How many degrees of freedom would the t-statistic have if the sample size had been 5? Exercise 8: A random sample of 20 purchases showed the following amounts (in
> For the regression of Exercise 2, find the standard error of the regression slope. Show all three values that go into the calculation. Exercise 2: A training center, wishing to demonstrate the effectiveness of their methods, tests some of their clients
> For the same reasons identified in Exercise 42, a friend of yours claims that the attendance at Road (away) games is lower in the American League than in the National League. Using the Attendance 2016 data (same data as in Exercises 42 and 44), you decid
> An investment blog suggests that you’ve been doing this all wrong and should invest in mutual funds only for the short term. So you decide to compare returns at 1 month and 3 months. a) Using the data provided, check the conditions for this test. b) Writ
> You have heard that if you leave your money in mutual funds for a longer period of time, you will see a greater return. So you would like to compare the 1-year and 5-year returns of a random sample of mutual funds to see if indeed, your return is expecte
> Using the results of the experiment described in Exercise 63, does it matter whether one listens to rap music while studying, or is it better to study without music at all? a) Test an appropriate hypothesis and state your conclusion. b) If you concluded
> A company is considering marketing their classical music as “music to study by.” Is this a valid slogan? In a study conducted by some statistics students, 62 people were randomly assigned to listen to rap music, music
> Given the test results on golf tees described in Exercise 61, is there evidence that balls hit off Stinger tees travel farther? Assume that 6 balls were hit off each tee and that the data are suitable for inference.
> Does it matter what kind of tee a golfer places the ball on? The company that manufactures “Stinger” tees claims that the thinner shaft and smaller head will lessen resistance and drag, reducing spin and allowing the b
> Financial analysts know that January credit card charges will generally be much lower than those of the month before. What about the difference between January and the next month? Does the trend continue? The dataset contains the monthly credit card char
> Spending on credit cards decreases after the Christmas spending season (as measured by amount charged on a credit card in December). The dataset with the same name as this exercise contains the monthly credit card charges of a random sample of 99 cardhol
> The Internet has revolutionized business and offers unprecedented opportunities for globalization. However, the ability to access the Internet varies greatly among different regions of the world. One of the variables the United Nations collects data on e
> Games for the iPad have a distribution of prices that is skewed to the high end. a) Explain why this is what you would expect. b) Members of the iPad gamers club each own about 50 games. Pat is one such member. What would you expect the shape of the di
> Examine the regression and scatterplot showing the regression line, 95% confidence intervals, and 95% prediction intervals using 2006 and 2010 energy use (kg oil equivalent per $1000 GDP) for a sample of 31 countries first examined in Exercise 54. The re
> Here is a scatterplot showing the regression line, 95% confidence intervals, and 95% prediction intervals, using 2015 and 2016 male unemployment data for a sample of 33 nations. The response variable is the 2016-Male Rate, and the predictor variable is t
> Here is a scatterplot showing the regression line, 95% confidence intervals, and 95% prediction intervals, using youth unemployment data for a sample of 33 nations. The response variable is the Male Rate, and the predictor variable is the Female Rate.
> The Great Recession of 2008 changed spending and energy use habits worldwide. Based on data collected from the United Nations Millennium Indicators Database related to measuring the goal of ensuring environmental sustainability, investigate the associati
> A sample of 61 model-2013 cars from an online information service was examined to see how fuel efficiency (as highway mpg) relates to the cost (Manufacturer’s Suggested Retail Price in dollars) of cars. (Data in All the efficiency) Here
> The analyst in Exercise 28 realized the data were in need of transformation because of the non-linearity between the variables. Economists commonly take the logarithm of these variables to make the relationship more nearly linear, and she did too. (These
> Using the same data provided in Exercise 48, answer the following questions. a) Find the 95% prediction interval for the effectiveness of the video on a pitcher with an initial ability of 33 strikes. b) Do you think predictions made by this regression wi
> Consider the high school SAT scores data from Exercise 31 once more. The mean Verbal score was 596.30 and the standard deviation was 99.52. a) Find a 90% confidence interval for the mean SAT Math score for all students with an SAT Verbal score of 500.
> Consider again the data in Exercise 29 about the fuel economy and weights of cars. a) Create a 95% confidence interval for the average fuel efficiency among cars weighing 2500 pounds, and explain what your interval means. b) Create a 95% prediction inte
> Ads for a Little League instructional video claimed that the techniques would improve the performances of Little League pitchers. To test this claim, 20 Little Leaguers threw 50 pitches each, and we recorded the number of strikes. After the players parti
> For each situation below identify the population and the sample and identify p and pn if appropriate and what the value of pn is. Would you trust a confidence interval for the true proportion based on these data? Explain briefly why or why not. a) As co
> Many factors may affect fans’ decision to go to a ball game. Is it possible that fans prefer teams with an older pitching staff? a) Examine a scatterplot of Attend/Game and PitchAge. Check the conditions for regression. b) Do you think there is a linear
> In Exercise 44, the company Zappos was omitted. Here is a scatterplot of the data with Zappos plotted as an x: a) In words, what does the outlying point say about Zappos? b) What effect would this point have on the regression, had it been left with t
> In Exercise 43, we examined the Worldwide Cost of Living Survey cost of living index. Now we use the Restaurant Price Index to predict total cost of living. Here are the results: a) How do you interpret the coefficient of Restaurant price? b) The R2 o
> Fortune Magazine publishes the top 100 companies to work for every year. Among the information listed is the percentage growth in jobs at each company. The output below shows the regression of job growth (%) in the current year on job growth from two yea
> The Worldwide Cost of Living Survey published by Numbeo.com provides an index that expresses the cost of living in other cities as a percentage of the New York cost. For example, in 2017, the cost of living index in Geneva was 142, which means that it wa
> There are 168 hours in a week. If you spend all of it sleeping and having fun, you will earn very little money. On the other hand, if you spend much of it working, do you earn more? In other words, do people earn more money each year when they work a gre
> In 2014, cnet.com listed the battery life (in hours) and maximum luminous intensity (i.e., screen brightness, in cd>m2) for a sample of tablet computers. We want to know if we can predict battery life from the maximum brightness. (reviews.cnet.com/830
> Using a statistics program, consider again the relationship between the sales and profits of Fortune 500 companies that you analyzed in Exercise 38. a) Find a 95% confidence interval for the slope of the regression line. Interpret your interval in conte
> Using a statistics program, consider again the relationship between the population and ozone level of U.S. cities that you analyzed in Exercise 37. a) Give a 90% confidence interval for the approximate increase in ozone level associated with each additi
> A business analyst was interested in the relationship between a company’s sales and its profits. She collected data (in millions of dollars) from a random sample of Fortune 500 companies and created the regression analysis and summary s
> A market researcher for a provider of iPhone accessories wants to know the proportion of customers who own cars to assess the market for a new iPhone dashboard mount. A survey of 500 customers indicates that 76% own cars. a) What is the standard deviati
> The Environmental Protection Agency is examining the relationship between the ozone level (in parts per million) and the population (in millions) of U.S. cities. Part of the regression analysis is shown. a) We suspect that the greater the population o
> Consider the high school SAT scores data from Exercise 31. a) Find a 90% confidence interval for the slope of the true line describing the association between Math and Verbal scores. b) Explain in this context what your confidence interval means.
> The Gallup organization has, over six decades, periodically asked the following question: If your party nominated a generally well-qualified person for president who happened to be a woman, would you vote for that person? We wonder if the proportion of t
> Football owners are constantly in competition for good players. The more wins, the more likely that the team will provide good business returns for the owners. The resources that each of the 32 teams has in the National Football League (NFL) vary, but th
> How strong is the association between labor productivity and labor costs? Data from the Bureau of Labor Statistics for labor productivity, as measured by Output per Employee, and Unit Labor Costs across industries, are used to examine this relationship (
> How strong was the association between student scores on the Math and Verbal sections of the old SAT? Scores on this exam ranged from 200 to 800 and were widely used by college admissions offices. Here are summary statistics, regression analysis, and plo
> Consumer Reports listed the price (in dollars) and power (in cold cranking amps) of auto batteries. We want to know if more expensive batteries are generally better in terms of starting power. Here are the regression and residual output, where the respon
> A consumer organization has reported test data for 50 car models. We will examine the association between the weight of the car (in thousands of pounds) and the fuel efficiency (in miles per gallon). Use the data provided on the disk to answer the follow
> A business analyst is looking at a company’s assets and sales to determine the relationship (if any) between the two measures. She has data (in $million) from a random sample of 79 Fortune 500 companies, and obtained the linear regressi
> A marketing researcher for a phone company surveys 100 people and finds that that proportion of clients who are likely to switch providers when their contract expires is 0.15. a) What is the standard deviation of the sampling distribution of the proport
> Based on the analysis of used car prices you did for Exercise 25, if appropriate, create a 95% confidence interval for the slope of the regression line and explain what your interval means in context.
> The following software results provide information about the size (in square feet) of 18 homes in Ithaca, New York, and the city’s assessed value of those homes, where the response variable is Assessment. a) Explain why inference for
> Classified ads in a newspaper offered several used Toyota Corollas for sale. Listed below are the ages of the cars and the advertised prices. a) Make a scatterplot for these data. b) Do you think a linear model is appropriate? Explain. c) Find the e
> Using unemployment data provided by the World Bank, investigate the association between the male unemployment rate in 2014 and 2017. a) Find a regression model predicting the 2017 rate from the 2014 rate. b) Examine the residuals to determine if a line
> The index of deflated turnover for retail trade shows the activity in volume of the retail trade sector. The United Nations Statistics Division reports Retail trade deflated sales/turnover (seasonally adjusted) with 2005 = 100. The data file holds this i
> The Brief Case for Chapter 4 listed the rate of return for 98 mutual funds over the previous 3-year and 5-year periods. It’s common for advertisements to carry the disclaimer that “past returns may not be indicative of future performance.” Do these data
> In an investigation of environmental causes of disease, data were collected on the annual mortality rate (deaths per 100,000) for males in 61 large towns in England and Wales. In addition, the water hardness was recorded as the calcium concentration (par
> Exercise 18 shows computer output examining the association between the sizes of houses and their sale prices. a) Check the assumptions and conditions for inference. b) Find a 95% confidence interval for the slope and interpret it.
> Exercise 17 shows computer output examining the association between the length of a movie and its cost. a) Check the assumptions and conditions for inference. b) Find a 95% confidence interval for the slope and interpret it.
> How does the price of a house depend on its size? Data from Saratoga, New York, on 1057 randomly selected houses that had been sold include data on price ($) and Living Area (ft2), producing the following graphs and computer output: a) Explain in words
> A tourist agency wants to know what proportion of visitors to the Eiffel Tower are from the Far East. To find out they survey 100 people in the line to purchase tickets to the top of the tower one Sunday afternoon in May. Are all the assumptions and cond
> How does the cost of a movie depend on its length? Data on the cost (millions of dollars) and the running time (minutes) for major release films in one recent year are summarized in these plots and computer output: a) Explain in words and numbers wh
> The earth has been getting warmer. Most climate scientists agree that one important cause of the warming is the increase in atmospheric levels of carbon dioxide (CO2), a greenhouse gas. Here is part of a regression analysis of the mean annual air tempera
> Several studies have found that the frequency with which shoppers browse Internet retailers is related to the frequency with which they actually purchase products and/or services online. Here are data showing the age of respondents and their answer to th
> For each of the following situations, state whether you’d use a chi-square goodness-of-fit test, a chi-square test of homogeneity, a chi-square test of independence, or some other statistical test. a) Is the quality of a car affected by what day it was
> For each of the following situations, state whether you’d use a chi-square goodness-of-fit test, chi square test of homogeneity, chi-square test of independence, or some other statistical test. a) A brokerage firm wants to see whether the type of accoun
> A marketing executive tested two incentives to see what percentage of customers would enroll in a new Web-based loyalty program. The customers were asked to log on to their accounts on the Web and provide some demographic and spending information. As an
> In 2010, the U.S. Congress passed the historic health care reform bill that will provide some type of coverage for the millions of Americans without health care insurance. Just how widespread is the lack of medical coverage in 2016, years after health ca
> You are on the financial planning team for monitoring a high spending segment of a credit card. You know that customers tend to spend more during December before the holidays, but you’re not sure about the pattern of spending in the months after the holi
> In Chapter 4, we examined the regression of the sales price of a home on its size and saw that larger homes generally fetch a higher price. How much can we learn about a house from the fact that it has a fireplace or more than the average number of bedro
> A philanthropic organization collects and buys data on their donor base. The full database contains about 4.5 million donors and over 400 variables collected (continued) on each, but the dataset Donor profiles is a sample of 916 donors and includes the v
> A real estate agent wants to know how many owners of homes worth over $1,000,000 might be considering putting their home on the market in the next 12 months. He surveys 40 of them and finds that 10 of them are considering such a move. Are all the assumpt
> Using the Paralyzed Veterans dataset, construct a 95% confidence interval for the mean age of a potential donor to the Paralyzed Veterans. Test the hypothesis that the mean age is 62 years old. Discuss what the confidence interval says about the hypothes
> In the last chapter, you looked at the data file Real estate sample 1200, which holds the following variables: • Sale Price (in $) • Lot size (size of the lot in acres) • Waterfront (Yes, No) • Age (in years) • Central Air (Yes, No) • Fuel Type (Wood, Oi
> A real estate agent is trying to understand the pricing of homes in her area, a region comprised of small to midsize towns and a small city. For each of 1200 homes recently sold in the region, the file Real estate sample 1200 holds the following variable
> Utilities must forecast the demand for energy use far into the future because it takes decades to plan and build new power plants. Ron Baker, who worked for New York State Electric and Gas (NYSEG), had the job of predicting the proportion of homes that w
> In 2011, when the Gallup organization polled investors, 34% rated gold the best long-term investment. But in April of 2017 Gallup surveyed a random sample of U.S. adults (news.gallup.com/poll/208820/americans-favor-real-estate-long-terminvestment.aspx).
> Every spring, Nenana, Alaska, hosts a contest in which participants try to guess the exact minute that a wooden tripod placed on the frozen Tanana River will fall through the breaking ice. The contest started in 1917 as a diversion for railroad engineers
> The product manager at a subsidiary of Kraft Foods, Inc., is interested in learning how sensitive sales are to changes in the unit price of a frozen pizza in Dallas, Denver, Baltimore, and Chicago. The product manager has been provided data on both Price
> In Exercise 59, we looked at the times in two different heats for the 800-m men’s run from the 2012 Olympics. Unlike track events, swimming heats are not determined at random. Instead, swimmers are seeded so that better swimmers are pla
> In Olympic running events, preliminary heats are determined by random draw, so we should expect the ability level of runners in the various heats to be about the same, on average. The table gives the times (in seconds) for the 800-m men’
> Here’s some additional information about the pizza sales data presented in Exercise 57. It is generally thought that sales spike during the weeks leading up to AFC and NFC football championship games, as well as leading up to the Super
> The proportion of adult women in the United States is approximately 51%. A marketing survey telephones 400 people at random. a) What is the sampling distribution of the observed proportion that are women? b) What is the standard deviation of that propo
> A national food product company believes that it sells more frozen pizza during the winter months than during the summer months. Average weekly sales for a sample of stores in the Baltimore area over a three-year period provided the following data for sa
> The average credit card debt carried by college students was compared at public versus private universities. It was reported that a significant difference existed between the two types of institutions and that students at private universities carried hig
> The National Assessment in Education Program compared science scores for students who had home Internet access with the scores of those who did not, as shown in the graph. They report that the differences are statistically significant. a) Explain what
> The U.S. Bureau of Economic Analysis provides information on the GDP in the United States by metropolitan area (www.bea.gov). The Bureau recently released figures that showed the percent change in real GDP by metropolitan area for 2004–
> The U.S. Bureau of Economic Analysis also provides information on the growth of the U.S. economy (www.bea.gov). The Bureau recently released figures that they claimed showed a growth spurt in the western region of the United States. Using the table and m
> The U.S. Bureau of Economic Analysis provides information on the Gross Domestic Product Per Capita (GDP PC) in the United States by state (www.bea.gov). The Bureau recently released figures that showed the real (GDP PC) by state for 2016. Using the data
> In a recent study of enterprise resource planning (ERP) system effectiveness, researchers asked companies about how they assessed the success of their ERP systems. Out of 335 manufacturing companies surveyed, they found that 201 used return on investment
> It has become more common for shoppers to “comparison shop” using the Internet. Respondents to a Pew survey in 2013 who owned cell phones were asked whether they had, in the past 30 days, looked up the price of a produ
> The Pew Internet & American Life Project routinely conducts surveys to gauge the impact of the Internet and technology on daily life. A recent survey asked respondents if they read online journals or blogs, an Internet activity of potential interest
> Every year, Fortune magazine lists the 100 best companies to work for, based on criteria such as pay, benefits, days off, and diversity. In 2018, the top three were Sales Force, Wegmans Food Markets, and Ultimate Softeware. In 2017, of the top 30, 10 wer
