Question: The U.S. government’s “Cash for

> From her firm’s computer telephone log, an executive found that the mean length of 64 telephone calls during July was 4.48 minutes with a standard deviation of 5.87 minutes. She vowed to make an effort to reduce the length of calls. The August phone log

> Are women’s feet getting bigger? Retailers in the last 20 years have had to increase their stock of larger sizes. Wal-Mart Stores, Inc., and Payless Shoe Source, Inc., have been aggressive in stocking larger sizes, and Nordstromâ&

> Has the cost to outsource a standard employee background check changed? A random sample of 10 companies in spring 2010 showed a sample average of $105 with a sample standard deviation equal to $32. A random sample of 10 different companies in spring 2012

> In 2009 Noodles & Company introduced spaghetti and meatballs to their menu. Before putting it on the menu, they performed taste tests to determine the best-tasting spaghetti sauce. In a paired comparison, 70 tasters were asked to rate their satisfaction

> Former U.S. Vice President Dick Cheney received a lot of publicity after his fourth heart attack. A portable defibrillator was surgically implanted in his chest to deliver an electric shock to restore his heart rhythm whenever another attack was threaten

> In San Francisco, a sample of 3,200 wireless routers showed that 1,312 used encryption (to prevent hackers from intercepting information). In Seattle, a sample of 1,800 wireless routers showed that 684 used encryption. (a). Set up hypotheses to test wh

> In a marketing class, 44 student members of virtual (Internet) project teams (group 1) and 42 members of face-to-face project teams (group 2) were asked to respond on a 1–5 scale to the question: “As compared to other teams, the members helped each other

> A study revealed that the 30-day readmission rate was 31.5 percent for 400 patients who received after-hospital care instructions (e.g., how to take their medications) compared to a readmission rate of 38.5 percent for 400 patients who did not receive su

> Does a “follow-up reminder” increase the renewal rate on a magazine subscription? A magazine sent out 760 subscription renewal notices (without a reminder) and got 703 renewals. As an experiment, they sent out 240 subscription renewal notices (with a rem

> Vail Resorts tracks the proportion of seasonal employees who are rehired each season. Rehiring a seasonal employee is beneficial in many ways, including lowering the costs incurred during the hiring process such as training costs. A random sample of 833

> At a University of Colorado woman’s home basketball game, a random sample of 25 concession purchases showed a mean of $7.12 with a standard deviation of $2.14. For the next week’s home game, the admission ticket had a discount coupon for popcorn printed

> A ski company in Vail owns two ski shops, one on the east side and one on the west side. Sales data showed that at the eastern location there were 56 pairs of large gloves sold out of 304 total pairs sold. At the western location there were 145 pairs of

> When the background music tempo was slow, the mean amount of bar purchases for a sample of 17 restaurant patrons was $30.47 with a standard deviation of $15.10. When the background music tempo was fast, the mean amount of bar purchases for a sample of 14

> After John F. Kennedy Jr. was killed in an airplane crash at night, a survey was taken, asking whether a noninstrument-rated pilot should be allowed to fly at night. Of 409 New York State residents, 61 said yes. Of 70 aviation experts who were asked the

> eShopNet, an online clothing retailer, is testing a new e-mail campaign by sending one version of the e-mail with the word “free” in the subject line (version A) to a group of 1500 customers and another version of the e-mail with the word “discount” in t

> How many full-page advertisements are found in a magazine? In an October issue of Muscle and Fitness, there were 252 ads, of which 97 were full-page. For the same month, the magazine Glamour had 342 ads, of which 167 were full-page. (a). Is the differe

> To test his hypothesis that students who finish an exam first get better grades, a professor kept track of the order in which papers were handed in. Of the first 25 papers, 10 received a B or better compared with 8 of the last 24 papers handed in. Is the

> A study of the Fortune 100 board of director members showed that there were 36 minority women holding board seats out of 202 total female board members. There were 142 minority men holding board seats out of 993 total male board members. (a). Treating

> A 2005 study found that 202 women held board seats out of a total of 1,195 seats in the Fortune 100 companies. A 2003 study found that 779 women held board seats out of a total of 5,727 seats in the Fortune 500 companies. Treating these as random samples

> Are college students more likely than young children to eat cereal? Researchers surveyed both age groups to find the answer. The results are shown in the table below. (a). State the hypotheses used to answer the question. (b). Using α =

> In an early home game, an NBA team made 66 of their 94 free throw attempts. In one of their last home games, the team made 68 of 89 attempts. (a). At α = .10, did the team significantly improve its free throw percentage (left-tailed test)? (b). Use Ex

> The top food snacks consumed by adults aged 18–54 are gum, chocolate candy, fresh fruit, potato chips, breath mints/candy, ice cream, nuts, cookies, bars, yogurt, and crackers. Out of a random sample of 25 men, 15 ranked fresh fruit in their top five sna

> In a bumper test, three test vehicles of each of three types of autos were crashed into a barrier at 5 mph, and the resulting damage was estimated. Crashes were from three angles: head-on, slanted, and rear-end. The results are shown below. Research ques

> The average mpg usage for a 2009 Toyota Prius for a sample of 10 tanks of gas was 45.5 with a standard deviation of 1.8. For a 2009 Honda Insight, the average mpg usage for a sample of 10 tanks of gas was 42.0 with a standard deviation of 2.3. (a). Assu

> Is a state’s income related to its high school dropout rate? Research question: Do the high school dropout rates differ among the five income quintiles? State High School Dropout Rates by Income Groups Lowest Income Quintile 2nd In

> The Environmental Protection Agency (EPA) advocates a maximum arsenic level in water of 10 micrograms per liter. Below are results of EPA tests on randomly chosen wells in a suburban Michigan county. Research question: Is the mean arsenic level affected

> An ANOVA study was conducted to compare dental offices in five small towns. The response variable was the number of days each dental office was open last year. Research question: Is there a difference in the means among these five towns? Dental Clin

> An MBA director examined GMAT scores for the first 10 MBA applicants (assumed to be a random sample of early applicants) for four academic quarters. Research question: Do the mean GMAT scores for early applicants differ by quarter? GMAT Scores of Fi

> Below are results of braking tests of the Ford Explorer on glare ice, packed snow, and split traction (one set of wheels on ice, the other on dry pavement), using three braking methods. Research question: Is the mean stopping distance affected by braking

> The results shown below are mean productivity measurements (average number of assemblies completed per hour) for a random sample of workers at each of three plants. Research question: Are the mean hourly productivity levels the same for workers in these

> The waiting time (in minutes) for emergency room patients with non-life-threatening injuries was measured at four hospitals for all patients who arrived between 6:00 and 6:30 p.m. on a certain Wednesday. The results are shown below. Research question: Ar

> In a bumper test, three types of autos were deliberately crashed into a barrier at 5 mph, and the resulting damage (in dollars) was estimated. Five test vehicles of each type were crashed, with the results shown below. Research question: Are the mean cra

> Mean output of solar cells of three types are measured six times under random light intensity over a period of 5 minutes, yielding the results shown. Research question: Is the mean solar cell output the same for all cell types? Solar Cell Output (wa

> The XYZ Corporation is interested in possible differences in days worked by salaried employees in three departments in the financial area. A survey of 23 randomly chosen employees reveals the data shown below. Because of the casual sampling methodology i

> Is there a difference in the average number of years’ seniority between returning part-time seasonal employees and returning full-time seasonal employees at a Vail Resorts’ ski mountain? From a random sample of 191 returning part-time employees, the aver

> Below are grade point averages for 25 randomly chosen university business students during a recent semester. Research question: Are the mean grade point averages the same for students in these four class levels? Grade Point Averages of 25 Business S

> Is the water on your airline flight safe to drink? It is not feasible to analyze the water on every flight, so sampling is necessary. The Environmental Protection Agency (EPA) found bacterial contamination in water samples from the lavatories and galley

> A 20-minute consumer survey mailed to 500 adults aged 25234 included a $5 Starbucks gift certificate. The same survey was mailed to 500 adults aged 25234 without the gift certificate. There were 65 responses from the first group and 45 from the second gr

> A survey of 100 mayonnaise purchasers showed that 65 were loyal to one brand. For 100 bath soap purchasers, only 53 were loyal to one brand. Perform a two-tailed test comparing the proportion of brand-loyal customers at α = .05.

> In 2006, a sample of 200 in-store shoppers showed that 42 paid by debit card. In 2009, a sample of the same size showed that 62 paid by debit card. (a) Formulate appropriate hypotheses to test whether the percentage of debit card shoppers increased. (b

> During the period 199021998 there were 46 Atlantic hurricanes, of which 19 struck the United States. During the period 199922006 there were 70 hurricanes, of which 45 struck the United States. (a) State the hypotheses to test whether the percentage of h

> Find the test statistic and do the two-sample test for equality of proportions. a. Repeat buyers at two car dealerships: p1 = .30, n1 = 50, p2 = .54, n2 = 50, α = .01, left-tailed test. b. Honor roll students in two sororities: p1 = .45, n1 = 80, p2 = .

> Find the sample proportions and test statistic for equal proportions. Find the p-value. a. Dissatisfied workers in two companies: x1 = 40, n1 = 100, x2 = 30, n2 = 100, α = .05, two tailed test. b. Rooms rented at least a week in advance at two hotels: x

> Calculate the test statistic and p-value for a test of equal population proportions. What is your conclusion? a. Left-tailed test, α = .10, x1 = 28, n1 = 336, x2 = 14, n2 = 112 b. Right-tailed test, α = .05, x1 = 276, n1 = 300, x2 = 440, n2 = 500 c. Two

> Calculate the test statistic and p-value for a test of equal population proportions. What is your conclusion? a. Right-tailed test, α = .10, x1 = 228, n1 = 240, x2 = 703, n2 = 760 b. Left-tailed test, α = .05, x1 = 36, n1 = 80, x2 = 66, n2 = 120 c. Two-

> Repeat the previous exercise, assuming unequal variances. Calculate the p-value using Excel, and show the Excel formula you used. Previous exercise: Do a two-sample test for equality of means assuming equal variances. Calculate the p-value. a. Compari

> A newly installed automatic gate system was being tested to see if the number of failures in 1,000 entry attempts was the same as the number of failures in 1,000 exit attempts. A random sample of eight delivery trucks was selected for data collection. Do

> Below is a random sample of shoe sizes for 12 mothers and their daughters. (a) At α = .01, does this sample show that women’s shoe sizes have increased? State your hypotheses and show all steps clearly. (b) Is the deci

> The coach told the high school swim team that times in the 200-yard individual medley in the Division I-AA Swim Championships typically are more than 1/2 second faster than their seed times going into the meet. At α = .05, do these times (i

> Blue Box is testing a new “half price on Tuesday” policy on DVD rentals at a sample of 10 locations. (a). At α = .10, do the data show that the mean number of Tuesday rentals has increased? (b). Is th

> In preliminary tests of a vaccine that may help smokers quit by reducing the “rush” from tobacco, 64 subjects who wanted to quit smoking were given either a placebo or the vaccine. Of the 32 in the placebo group, only 3 quit smoking for 30 days (the U.S.

> A 20-minute consumer survey mailed to 500 adults aged 25–34 included a $5 Starbucks gift certificate. The same survey was mailed to 500 adults aged 25–34 without the gift certificate. There were 65 responses from the first group and 45 from the second gr

> A survey of 100 mayonnaise purchasers showed that 65 were loyal to one brand. For 100 bath soap purchasers, only 53 were loyal to one brand. Form a 95 percent confidence interval for the difference of proportions. Does it include zero?

> This table shows partial results for a one-factor ANOVA, (a). Calculate the F test statistic. (b). Calculate the p-value using Excel’s function 5F.DIST.RT (F,DF1,DF2). (c). Find the critical value F.05 from Appendix F or using Excel

> A manufacturing process drills holes in sheet metal that are supposed to be .5000 cm in diameter. Before and after a new drill press is installed, the hole diameter is carefully measured (in cm) for 12 randomly chosen parts. At α = .05, do

> An experimental surgical procedure is being studied as an alternative to the old method. Both methods are considered safe. Five surgeons perform the operation on two patients matched by age, sex, and other relevant factors, with the results shown. The ti

> The American Bankers Association reported that, in a sample of 120 consumer purchases in France, 60 were made with cash, compared with 26 in a sample of 50 consumer purchases in the United States. Construct a 90 percent confidence interval for the differ

> Consider a one-factor ANOVA with n1 = 6, n2 = 5, n3 = 4, n4 = 6, n5 = 4. (a). How many possible comparisons of means are there? (b). State the degrees of freedom for Tukey’s T. (c). Find the critical value of Tukey’s T for α = .05.

> Consider a one-factor ANOVA with n1 = 9, n2 = 10, n3 = 7, n4 = 8. (a). How many possible comparisons of means are there? (b). State the degrees of freedom for Tukey’s T. (c). Find the critical value of Tukey’s T for α = .05.

> For each data set: (a) State the hypotheses. (b) Use Excel’s Data Analysis (or MegaStat or MINITAB) to perform the one-factor ANOVA, using α = .05. (c) State your conclusion about the population means. (d) Interpret th

> For each data set: (a) State the hypotheses. (b) Use Excel’s Data Analysis (or MegaStat or MINITAB) to perform the one-factor ANOVA, using α = .05. (c) State your conclusion about the population means. (d) Interpret th

> For each data set: (a) State the hypotheses. (b) Use Excel’s Data Analysis (or MegaStat or MINITAB) to perform the one-factor ANOVA, using α = .05. (c) State your conclusion about the population means. (d) Interpret th

> For each data set: (a) State the hypotheses. (b) Use Excel’s Data Analysis (or MegaStat or MINITAB) to perform the one-factor ANOVA, using α = .05. (c) State your conclusion about the population means. (d) Interpret th

> In a one-factor ANOVA with sample sizes n1 = 8, n2 = 5, n3 = 6, n4 = 6, the test statistic was Fcalc = 3.251. (a). State the hypotheses. (b). State the degrees of freedom for the test. (c). What is the critical value of F for α = .05? (d). What is y

> In a one-factor ANOVA with sample sizes n1 = 5, n2 = 7, n3 = 6, n4 = 7, n5 = 5, the test statistic was Fcalc = 2.447. (a). State the hypotheses. (b). State the degrees of freedom for the test. (c). What is the critical value of F for α = .10? (d). W

> Oxnard Petro, Ltd. has three suppliers of catalysts. Orders are placed with each supplier every 15 working days, or about once every 3 weeks. The delivery time (days) is recorded for each order over 1 year. Are the main effects significant? Is there an i

> (a) At α = .05, does the following sample show that daughters are taller than their mothers? (b) Is the decision close? (c) Why might daughters tend to be taller than their mothers? Why might they not? Daughter's Height (cm) Mother's

> A market research firm is testing consumer reaction to a new shampoo on four age groups in four regions. There are five consumers in each test panel. Each consumer completes a 10-question product satisfaction instrument with a 5-point scale (5 is the hig

> Oxnard Petro, Ltd., has three interdisciplinary project development teams that function on an ongoing basis. Team members rotate from time to time. Every 4 months (three times a year) each department head rates the performance of each project team (using

> A small independent stock broker has created four sector portfolios for her clients. Each portfolio always has five stocks that may change from year to year. The volatility (coefficient of variation) of each stock is recorded for each year. Are the main

> A beer distributor is comparing quarterly sales of Coors Light (number of six-packs sold) at three convenience stores. Does this sample provide sufficient evidence to conclude that there is a significant difference in treatment means? Store 1 Store

> Five statistics professors are using the same textbook with the same syllabus and common exams. At the end of the semester, the department committee on instruction looked at average exam scores. Does this sample provide sufficient evidence to conclude th

> Engineers are testing company fleet vehicle fuel economy (miles per gallon) performance by using different types of fuel. One vehicle of each size is tested. Does this sample provide sufficient evidence to conclude that there is a significant difference

> Concerned about Friday absenteeism, management examined absenteeism rates for the last three Fridays in four assembly plants. Does this sample provide sufficient evidence to conclude that there is a significant difference in treatment means? Plant 1

> For each data set, use Hartley’s test to test the hypothesis of equal variances, using the 5 percent table of critical values from Table 11.5 and the largest and smallest sample variances from your previous ANOVA. Optional challenge: If

> Using the following Excel results: (a). What was the overall sample size? (b). How many groups were there? (c). Write the hypotheses. (d). Find the critical value of F for α = .10. (e). Calculate the test statistic. (f). Do the popu

> For each data set, use Hartley’s test to test the hypothesis of equal variances, using the 5 percent table of critical values from Table 11.5 and the largest and smallest sample variances from your previous ANOVA. Optional challenge: If

> Construct a 95 percent confidence interval for the difference of mean monthly rent paid by undergraduates and graduate students. What do you conclude? Undergraduate Student Rents (n = 10) 820 780 870 670 800 790 810 680 1,000 730 Graduate Student Re

> For each data set, use Hartley’s test to test the hypothesis of equal variances, using the 5 percent table of critical values from Table 11.5 and the largest and smallest sample variances from your previous ANOVA. Optional challenge: If

> For each data set, use Hartley’s test to test the hypothesis of equal variances, using the 5 percent table of critical values from Table 11.5 and the largest and smallest sample variances from your previous ANOVA. Optional challenge: If

> In a one-factor ANOVA with n1 = 7, n2 = 6, n3 = 5, n4 = 5, and n5 = 7, the sample standard deviations were s1 = 12, s2 = 24, s3 = 16, s4 = 46, and s5 = 27. For Hartley’s test: (a). State the hypotheses. (b). Calculate the degrees of freedom. (c). Fin

> In a one-factor ANOVA with n1 = 6, n2 = 4, and n3 = 5, the sample variances were s12 =121, s22 = 929, and s32 5 456. For Hartley’s test: (a). State the hypotheses. (b). Calculate the degrees of freedom. (c). Find the critical value at the 5 percent l

> Use MegaStat, MINITAB, or another software package to perform Tukey’s test for significant pairwise differences. Perform the test using both the 5 percent and 1 percent levels of significance. Refer to Exercise 11.8. Which pairs of mea

> Use MegaStat, MINITAB, or another software package to perform Tukey’s test for significant pairwise differences. Perform the test using both the 5 percent and 1 percent levels of significance. Refer to Exercise 11.7. Which pairs of mea

> Use MegaStat, MINITAB, or another software package to perform Tukey’s test for significant pairwise differences. Perform the test using both the 5 percent and 1 percent levels of significance. Refer to Exercise 11.6. Which pairs of mea

> Examine the data below showing the weights (in pounds) of randomly selected checked bags for an airline’s flights on the same day. (a) At α 5 = .05, is the mean weight of an international bag greater? Show the hypothese

> Use MegaStat, MINITAB, or another software package to perform Tukey’s test for significant pairwise differences. Perform the test using both the 5 percent and 1 percent levels of significance. Refer to Exercise 11.5. Which pairs of mea

> Researchers at the Mayo Clinic have studied the effect of sound levels on patient healing and have found a significant association (louder hospital ambient sound level is associated with slower postsurgical healing). Based on the Mayo Clinic’s experience

> In trials of an experimental Internet-based method of learning statistics, pre-tests and post-tests were given to two groups: traditional instruction (22 students) and Internet-based (17 students). Pre-test scores were not significantly different. On the

> Which samples show unequal variances? Use α = .05 in all tests. Show the critical values and degrees of freedom clearly and illustrate the decision rule. a. s1 = 5.1, n1 = 11, s2 = 3.2, n2 = 8, two-tailed test b. s1 = 221, n1 = 8, s2 = 445, n2 = 8, left

> Which samples show unequal variances? Use α = .10 in all tests. Show the critical values and degrees of freedom clearly and illustrate the decision rule. a. s1 = 10.2, n1 = 22, s2 = 6.4, n2 = 16, two-tailed test b. s1 = 0.89, n1 = 25, s2 = 0.67, n2 = 18

> A survey of 100 cigarette smokers showed that 71 were loyal to one brand, compared to 122 of 200 toothpaste users. Construct a 90 percent confidence interval for the difference in proportions.

> A study showed that 36 of 72 cell phone users with a headset missed their exit, compared with 12 of 72 talking to a passenger. Construct a 95 percent confidence interval for the difference in proportions.

> Using the following Excel results: (a). What was the overall sample size? (b). How many groups were there? (c). Write the hypotheses. (d). Find the critical value of F for α = .05. (e). Calculate the test statistic. (f). Do the popu

> A 30-minute consumer survey mailed to 500 adults aged 25234 included a $10 gift certificate to Borders. The same survey was mailed to 500 adults aged 25234 without the gift certificate. There were 185 responses from the first group and 45 from the second

> From a telephone log, an executive finds that 36 of 128 incoming telephone calls last week lasted at least 5 minutes. She vows to make an effort to reduce the length of time spent on calls. The phone log for the next week shows that 14 of 96 incoming cal

> In 2009, a sample of 200 in-store shoppers showed that 42 paid by debit card. In 2012, a sample of the same size showed that 62 paid by debit card. (a). Formulate appropriate hypotheses to test whether the percentage of debit card shoppers increased by

> When tested for compliance with Sarbanes-Oxley requirements for financial records and fraud protection, 14 of 180 publicly traded business services companies failed, compared with 7 of 67 computer hardware, software, and telecommunications companies. (a

> Are large companies more profitable per dollar of assets? The largest 500 companies in the world were ranked according to their number of employees, with groups defined as follows: Small = under 25,000 employees, Medium = 25,000 to 49,999 employees, Larg

> A special bumper was installed on selected vehicles in a large fleet. The dollar cost of body repairs was recorded for all vehicles that were involved in accidents over a 1-year period. Those with the special bumper are the test group and the other vehic