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Instructor's Resource Guide Understandable Statistics, 9/e 128 CHAPTER 9 TEST FORM A PAGE 1 For each of the following problems, please provide the requested information. (a) What is the level of significance? State the null and alternate hypotheses. Will you use a left-tailed, right-tailed, or two-tailed test? (b) Identify the sampling distribution you will use: the standard normal or the Student’s t. Explain the rationale for your choice. What is the value of the sample test statistic? (c) Find (or estimate) the P value. Sketch the sampling distribution and show the area corresponding to the P value. (d) Find the critical value(s). (e) Based on your answers for parts (a) to (d), will you reject or fail to reject the null hypothesis? Interpret your decision in the context of the application. 1. A large furniture store has begun a new ad campaign on local television. Before the campaign, the longterm average daily sales were $24,819. A random sample of 40 days during the new ad campaign gave a sample mean daily sale average of x = $25,910. Does this indicate that the population mean daily sales are now more than $24,819? Use a 1% level of significance. Assume = $1917. 1. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Part III: Sample Chapter Tests and Answers CHAPTER 9 TEST 129 FORM A PAGE 2 2. A new bus route has been established between downtown Denver and Englewood (a suburb of Denver). Dan has taken the bus to work for many years. For the old bus route, he knows from long experience that the mean waiting time between buses at his stop was = 20 minutes. However, a random sample of five waiting times between buses using the new route had mean x = 15.1 minutes with sample standard deviation s = 6.2 minutes. Does this indicate that the population mean waiting time for the new route is shorter than what it used to be? Use = 0.05. Assume that x is normally distributed. 2. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ 3. The State Fish and Game Division claims that 75% of the fish in Homestead Creek are rainbow trout. However, the local fishing club caught 189 fish one weekend and found that 125 were rainbow trout. For this problem, assume that no single fish was caught more than once. Does this indicate that the percentage of rainbow trout in Homestead Creek is less than 75%? Use = 0.01. 3. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Instructor's Resource Guide Understandable Statistics, 9/e 130 CHAPTER 9 TEST FORM A PAGE 3 4. A telemarketer is trying two different sales pitches to sell a carpet cleaning service. For his aggressive sales pitch, 175 people were contacted by phone, and 62 of those people bought the cleaning service. For his passive sales pitch, 154 people were contacted by phone, and 45 of those people bought the cleaning service. Does this indicate that there is any difference in the population proportions of people who will buy the cleaning service depending on which sales pitch is used? Use = 0.05. 4. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ 5. A systems specialist has studied the workflow of clerks doing the same inventory work. Based on this study, she designed a new workflow layout for the inventory system. To compare average production for the old and new methods, six clerks were randomly selected for the study. The average production rate for each clerk was recorded before and after the new system was introduced. The results are shown below. Test the claim that the new system increases the mean number of items process per shift. Use = 0.05. Clerk B: Old A: New Joe 116 123 Jon 108 114 Joy 93 112 Jen 88 82 Jan 119 127 Job 111 122 5. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Part III: Sample Chapter Tests and Answers CHAPTER 9 TEST 131 FORM A PAGE 4 6. How productive are employees? One way to answer this question is to study annual company profits per employee. Let x1 represent annual profits per employee in computer stores in St. Louis. A random sample of n1 = 11 computer stores gave a sample mean of x1 = 25.2 thousand dollars profit per employee with sample standard deviation s1 = 8.4 thousand dollars. Another random sample of n2 = 9 building supply stores in St. Louis gave a sample mean x2 = 19.9 thousand dollars per employee with sample standard deviation s2 = 7.6 thousand dollars. Does this indicate that in St. Louis, computer stores tend to have higher mean profits per employee? Use = 0.01. 6. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ 7. Do organic farming methods cause a change in produce size? A random sample of n1 = 89 organically grown tomatoes had sample mean weight x1 = 3.8 ounces. Another random sample of n2 = 75 tomatoes that were not grown organically had sample mean weight x2 = 4.1 ounces. Previous studies show that 1 0.9 ounce and 2 1.5 ounces. Does this indicate a difference between population mean weights of organically grown tomatoes compared with those not grown organically? Use a 5% level of significance. 7. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Instructor's Resource Guide Understandable Statistics, 9/e 132 CHAPTER 9 TEST FORM A PAGE 5 8. How tall are college hockey players? The average height has been 68.3 inches. A random sample of 14 hockey players gave a mean height of 69.1 inches. We may assume that x has a normal distribution with = 0.9 inch. Does this indicate that the population mean height is different from 68.3 inches? Use 5% level of significance. 8. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ 9. How long does it take to have food delivered? A Chinese restaurant advertises that the average delivery time will be no more than 30 minutes. A random sample of delivery times (in minutes) is shown below. Based on this sample, is the average delivery time greater than 30 minutes? Use a 5% level of significance. Assume that the distribution of times is normal. 32 39 28 32 21 28 39 42 30 25 27 26 29 30 9. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Part III: Sample Chapter Tests and Answers CHAPTER 9 TEST 133 FORM A PAGE 6 10. A music teacher knows from past records that 60% of students taking summer lessons play the piano. The instructor believes that this proportion may have dropped owing to the popularity of wind and brass instruments. A random sample of 80 students yielded 43 piano players. Test the instructor’s claim at = 0.05. 10. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Instructor's Resource Guide Understandable Statistics, 9/e 134 CHAPTER 9 TEST FORM B PAGE 1 For each of the following problems, please provide the requested information. (a) What is the level of significance? State the null and alternate hypotheses. Will you use a left-tailed, right-tailed, or two-tailed test? (b) Identify the sampling distribution you will use: the standard normal or the Student’s t. Explain the rationale for your choice. What is the value of the sample test statistic? (c) Find (or estimate) the P value. Sketch the sampling distribution and show the area corresponding to the P value. (d) Find the critical value(s). (e) Based on your answers for parts (a) to (d), will you reject or fail to reject the null hypothesis? Interpret your decision in the context of the application. 1. Long-term experience shows that after laser eye surgery, the mean recovery time is = 5.3 days. However, a random sample of 32 patients with this surgery had a sample mean recovery time of x = 4.2 days. Does this indicate that the mean recovery time is dropping? Use a 1% level of significance. Assume = 1.9 days. 1. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Part III: Sample Chapter Tests and Answers CHAPTER 9 TEST 135 FORM B PAGE 2 2. Recently, the national average yield on municipal bonds has been = 4.19%. A random sample of 16 Arizona municipal bonds gave an average yield of 5.11% with sample standard deviation of s = 1.15%. Does this indicate that the population mean yield for all Arizona municipal bonds is greater than the national average? Use a 5% level of significance. Assume that x is normally distributed. 2. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ 3. At a local four-year college, 37% of the student body is composed of freshmen. A random sample of 42 student names taken from the dean’s list over the past several semesters showed that 17 were freshmen. Does this indicate that the population proportion of freshmen on the dean’s list is different from 37%? Use a 1% level of significance. 3. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Instructor's Resource Guide Understandable Statistics, 9/e 136 CHAPTER 9 TEST FORM B PAGE 3 4. In a random sample of 62 students, 34 said that they would vote for Jennifer as student body president. In another random sample of 77 students, 48 said they would vote for Kevin as student body president. Does this indicate that in the population of all students, Kevin has a higher proportion of votes? Use = 0.05. 4. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ 5. Five members of the college track team in Denver (elevation 5,200 feet) went up to Leadville (elevation 10,152 feet) for a track meet. The times in minutes for these team members to run 2 miles at each location are shown below. Team member Denver Leadville Ojai 10.7 11.5 Edgar 9.1 10.6 Euclid 11.4 11.0 Seymour 9.7 11.2 Sylvia 9.2 10.3 Assume that the team members constitute a random sample of track team members. Use a 5% level of significance to test the claim that the times were longer at the higher elevation. 5. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Part III: Sample Chapter Tests and Answers CHAPTER 9 TEST 137 FORM B PAGE 4 6. Two models of a popular pickup truck are tested for miles per gallon (mpg) gasoline consumption. The Pacer model was tested using a random sample of n1 = 9 trucks, and the sample mean was x1 = 27.3 mpg with sample standard deviation s1 = 6.2 mpg. The Road Runner model was tested using a random sample of n2 = 14 trucks. The sample mean was x2 = 22.5 mpg with sample standard deviation s2 = 6.8 mpg. Does this indicate that the population mean gasoline consumption for the Pacer is higher than that of the Road Runner? Use = 0.01. 6. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ 7. Students at the college agricultural research station are studying egg production of free-range chickens compared with caged chickens. During a 1-week period, a random sample of n1 = 93 free-range hens produced an average of x1 = 11.2 eggs per hen. For the same period, another random sample of n2 = 87 caged hens produced a sample average of x2 = 8.5 eggs per hen. Previous studies show that 1 4.4 eggs and 2 5.7 eggs. Does this indicate the population mean egg production for free-range hens is higher? Use a 5% level of significance. 7. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Instructor's Resource Guide Understandable Statistics, 9/e 138 CHAPTER 9 TEST FORM B PAGE 5 8. How long does it take juniors to complete a standardized exam? The long-term average is believed to be 2.8 hours. We may assume that x has a normal distribution with = 0.8 hour. A random sample of 12 juniors gave a sample mean of x = 2.2 hours. Does this indicate that the population mean time is different from 2.8 hours? Use 5% level of significance. 8. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ 9. The owner of a comedy club has based business decisions on the average age of customers historically being 30 years. A random sample of customer ages is shown below. Based on this sample, is the average age more than 30 years? Use a 5% level of significance. Assume that the distribution of ages is normal. 37 43 30 27 26 39 35 38 45 46 42 21 51 28 40 20 9. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Part III: Sample Chapter Tests and Answers CHAPTER 9 TEST 139 FORM B PAGE 6 10. The department of transportation in a particular city knows from past records that 27% of workers in the downtown district use the subway system each day to commute to and from work. The department suspects that this proportion has increased owing to decreased parking spaces in the downtown district. A random sample of 130 workers in the downtown district showed that 49 used the subway daily. Test the claim at the 5% level of significance. 10. (a) __________________________ (b) __________________________ (c) (d) __________________________ (e) __________________________ Copyright © Houghton Mifflin Company. All rights reserved. Instructor's Resource Guide Understandable Statistics, 9/e 140 CHAPTER 9 TEST FORM C PAGE 1 Write the letter of the response that best answers each problem. 1. A small electronics store has begun to advertise in the local newspaper. Before advertising, the long-term average weekly sales were $9,820. A random sample of 50 weeks while the newspaper ads were running gave a sample mean weekly sales of x = $10,960. Does this indicate that the population mean weekly sales is now more than $9,820? Test at the 5% level of significance. Assume = $1,580. A. State the null and alternate hypotheses. 1. A. __________ (a) H0: = 9,820; H1: < 9,820 (b) H0: = 9,820; H1: > 9,820 (c) H0: x = 10,960; H1: x > 10,960 (d) H0: = 10,960; H1: > 10,960 (e) H0: > 9,820; H1: = 9,820 B. Compute the z or t value of the sample test statistic. (a) z = 5.10 (b) z = 0.10 (c) t = 0.72 (d) z = –5.10 B. __________ (e) t = –0.10 C. Find the P value or an interval containing the P value for the sample test statistic. (a) P value = 0.236 (b) P value = 0.460 (c) P value < 0.0001 (d) P value > 0.0001 (e) Cannot determine D. Find the critical value(s). D. __________ (a) z0 = 2.33 (b) z0 = 1.96 (c) t0 = –1.96 (d) z0 = 1.645 (e) t0 = –1.96 E. Based on your answers for parts A–D, what is your decision? (a) Do not reject H0 C. __________ (b) Reject H0 E. __________ (c) Cannot determine Copyright © Houghton Mifflin Company. All rights reserved. Part III: Sample Chapter Tests and Answers CHAPTER 9 TEST 141 FORM C PAGE 2 2. The average annual salary of employees at Wintertime Sports was $28,750 last year. This year the company opened another store. Suppose that a random sample of 18 employees gave an average annual salary of x = $25,810 with sample standard deviation s = $4,230. Use a 1% level of significance to test the claim that the average annual salary for all employees is different from last year’s average salary. Assume that salaries are normally distributed. A. State the null and alternate hypotheses. 2. A. __________ (a) H0: = 28,750; H1: < 28,750 (b) H0: = 25,810; H1: 25,810 (c) H0: 1 =2; H1: 1 2 (d) H0: x = 25,810; H1: x 25,810 (e) H0: = 28,750; H1: ≠ 28,750 B. Compute the z or t value of the sample test statistic. (a) t = –2.95 (b) z = –2.95 (c) t = –2.87 (d) z = –12.51 B. __________ (e) t = 2.95 C. Find the P value or an interval containing the P value for the sample test statistic. (a) Cannot determine (b) 0.01 < P value < 0.02 (c) P value < 0.010 (d) P value > 0.010 (e) P value < 0.005 D. Find the critical value(s). D. __________ (a) t0 = 2.58 (b) t0 = 1.96 (c) t0 = 2.567 (d) t0 = 2.898 (e) z0 = –2.567 E. Based on your answers for parts A–D, what is your decision? (a) Do not reject H0 C. __________ (b) Reject H0 Copyright © Houghton Mifflin Company. All rights reserved. (c) Cannot determine E. __________ Instructor's Resource Guide Understandable Statistics, 9/e 142 CHAPTER 9 TEST FORM C PAGE 3 3. The owner of Prices Limited claims that 75% of all the items in the store cost less than $5. Suppose that you check a random sample of 146 items in the store and find that 105 cost less than $5. Does this indicate that the proportion of items in the store that cost less than $5 is different from 75%? Use = 0.01. A. State the null and alternate hypotheses. 1. A. __________ (a) H0: p1 = p2; H1: p1 p2 (b) H0: p = 5; H1: p 5 (c) H0: p̂ = 0.75; H1: p̂ 0.75 (d) H0: p = 0.75; H1: p 0.75 (e) H0: p̂ = 0.72; H1: p̂ 0.72 B. Compute the z or t value of the sample test statistic. (a) t = –0.86 (b) t = –0.73 (c) z = –0.73 (d) z = 0.86 B. __________ (e) z = –0.86 C. Find the P value or an interval containing the P value for the sample test statistic. (a) P value = 0.2327 (b) P value = 0.0975 (c) P value = 0.3898 (d) P value = 0.1949 (e) P value = 0.8051 D. Find the critical value(s). D. __________ (a) z0 = 2.58 (b) z0 = –2.33 (c) z0 = 1.96 (d) t0 = –1.645 (e) t0 = 2.58 E. Based on your answers for parts A–D, what is your decision? (a) Do not reject H0 C. __________ (b) Reject H0 E. __________ (c) Cannot determine Copyright © Houghton Mifflin Company. All rights reserved. Part III: Sample Chapter Tests and Answers CHAPTER 9 TEST 143 FORM C PAGE 4 4. A random sample of 257 dog owners was taken 10 years ago, and it was found that 146 owned more than one dog (Sample 1). Recently, a random sample of 380 dog owners showed that 200 owned more than one dog (Sample 2). Do these data indicate that the proportion of dog owners owning more than one dog has decreased? Use a 5% level of significance. A. State the null and alternate hypotheses. 4. A. __________ (a) H0: p̂1 = p̂2 ; H1: p̂1 > p̂2 (b) H0: p1 = p2; H1: p1 < p2 146 (d) H0: p1 = p2; H1: p1 p2 (c) H0: p1 = 257 = 0.57; H1: p1 < 0.57 (e) H0: p1 = p2; H1: p1 > p2 B. Compute the z or t value of the sample test statistic. (a) z = 0.04 (b) z = 1.04 (c) z = 0.08 (d) t = 0.08 B. __________ (e) t = 1.04 C. Find the P value or an interval containing the P value for the sample test statistic. (a) P value = 0.8508 (b) P value = 0.4681 (c) P value = 0.2984 (d) P value = 0.4840 (e) P value = 0.1492 D. Find the critical value(s). D. __________ (a) t0 = 1.96 (b) z0 = 2.33 (c) t0 = –1.645 (d) z0 = 1.645 (e) z0 = 1.96 E. Based on your answers for parts A–D, what is your decision? (a) Do not reject H0 C. __________ (b) Reject H0 Copyright © Houghton Mifflin Company. All rights reserved. (c) Cannot determine E. __________ Instructor's Resource Guide Understandable Statistics, 9/e 144 CHAPTER 9 TEST FORM C PAGE 5 5. Seven manufacturing companies agreed to implement a time-management program in hopes of improving productivity. The average times, in minutes, it took the companies to produce the same piece of equipment are listed below. Does this information indicate that the program decreased production time? Assume normal population distributions. Use = 0.05. Company Before program (1) After program (2) 1 75 70 2 112 110 3 89 88 4 95 100 5 80 80 6 105 100 A. State the null and alternate hypotheses. 7 110 99 5. A. __________ (a) H0: 1 = 2; H1: 1 > 2 (b) H0: d = 0; H1: d 0 (c) H0: 1 = 2; H1: 1 < 2 (d) H0: d = 0; H1: d > 0 (e) H0: = 0; H1: < 0 B. Compute the z or t value of the sample test statistic. (a) t = 0 (b) z = 0.36 (c) t = 1.44 (d) t = 0.36 B. __________ (e) z = –1.44 C. Find the P value or an interval containing the P value for the sample test statistic. (a) P value = 0.1498 (b) P value ≈ 0.10 (c) P value = 0.0749 (d) P value > 0.250 (e) Cannot determine D. Find the critical value(s). D. __________ (a) t0 = 2.447 (b) t0 = 1.782 (c) t0 = 1.895 (d) z0 = 1.645 (e) t0 = 1.943 E. Based on your answers for parts A–D, what is your decision? (a) Do not reject H0 C. __________ (b) Reject H0 E. __________ (c) Cannot determine Copyright © Houghton Mifflin Company. All rights reserved. Part III: Sample Chapter Tests and Answers CHAPTER 9 TEST 145 FORM C PAGE 6 6. An independent rating service is trying to determine which of two film-developing shops has quicker service. Over a period of 12 randomly selected times, the average waiting period to develop a 24-exposure roll sold at Speedy Development is 58 minutes with standard deviation 3.5 minutes. The average waiting period at The Shutterbug to develop a 24-exposure roll over a period of 8 randomly selected times is 53 minutes with standard deviation 4.9 minutes. Using a 1% level of significance, can we say that there is a difference in the average waiting time between the two shops? A. State the null and alternate hypotheses. 6. A. __________ (a) H0: x1 = x2 ; H1: x1 x2 (b) H0: 1 =2; H1: 1 2 (c) H0: 1 = 2; H1: 1 > 2 (d) H0: = 58; H1: 58 (e) H0: d > 0; H1: d 0 B. Compute the z or t value of the sample test statistic. (a) z = 2.67 (b) t = 2.49 (c) t0 = 2.67 (d) z = 2.49 B. __________ (e) t = 2.67 C. Find the P value or an interval containing the P value for the sample test statistic. (a) 0.010 < P value < 0.025 (b) 0.02 < P value < 0.05 (c) Cannot determine (d) 0.01 < P value < 0.02 C. __________ (e) 0.005 < P value < 0.010 D. Find the critical value(s). D. __________ (a) t0 = 3.499 (b) z0 = 2.56 (c) z0 = 1.96 (d) t0 = 2.552 (e) Not listed E. Based on your answers for parts A–D, what is your decision? (a) Do not reject H0 (b) Reject H0 Copyright © Houghton Mifflin Company. All rights reserved. (c) Cannot determine E. __________ Instructor's Resource Guide Understandable Statistics, 9/e 146 CHAPTER 9 TEST FORM C PAGE 7 7. The personnel manager of a large retail clothing store suspects a difference in the mean amount of break time taken by workers during the weekday shifts compared with that of the weekend shifts. It is suspected that the weekday workers take longer breaks on average. A random sample of 46 weekday workers had a mean x1 = 53 minutes of break time per 8-hour shift. A random sample of 40 weekend workers had a mean x2 = 47 minutes. Previous studies show that 1 7.3 minutes and 2 9.1 minutes. Test the manager’s suspicion at the 5% level of significance. A. State the null and alternate hypotheses. 7. A. __________ (a) H0: 1 = 2; H1: 1 < 2 (b) H0: 1 = 2; H1: 1 > 2 (c) H0: 1 = 2; H1: 1 2 (d) H0: x1 = x2 ; H1: x1 > x2 (e) H0: d = 0; H1: d > 0 B. Compute the z or t value of the sample test statistic. (a) t = 3.34 (b) t = 0.73 (c) z = 0.73 (d) z = 1.645 B. __________ (e) z = 3.34 C. Find the P value or an interval containing the P value for the sample test statistic. (a) Cannot determine (b) P value = 0.0495 (c) P value = 0.0008 (d) P value = 0.0004 (e) P value = 0.2327 D. Find the critical value(s). D. __________ (a) t0 = 1.645 (b) t0 = 1.96 (c) z0 = 1.645 (d) z0 = 3.34 (e) z0 = 2.33 E. Based on your answers for parts A–D, what is your conclusion? (a) Do not reject H0 C. __________ (b) Reject H0 E. __________ (c) Cannot determine Copyright © Houghton Mifflin Company. All rights reserved. Part III: Sample Chapter Tests and Answers CHAPTER 9 TEST 147 FORM C PAGE 8 8. A machine in the lodge at a ski resort dispenses a hot-chocolate drink. The average cup of hot chocolate is supposed to contain 7.75 ounces. We may assume that x has a normal distribution with = 0.3 ounce. A random sample of 16 cups of hot chocolate from this machine shows the average content to be 7.62 ounces. Do you think that the machine is out of adjustment and that the average amount of hot chocolate is less than it is supped to be? Use a 5% level of significance. A. State the null and alternate hypotheses. 8. A. __________ (a) H0: 1 = 2; H1: 1 < 2 (b) H0: = 7.75; H1: 7.75 (c) H0: x = 7.62; H1: x < 7.62 (d) H0: > 7.62; H1: = 7.62 (e) H0: = 7.75; H1: < 7.75 B. Compute the z or t value of the sample test statistic. (a) t = –1.73 (b) z = –1.645 (c) z = –1.73 (d) t = –0.03 B. __________ (e) z = –0.03 C. Find the P value or an interval containing the P value for the sample test statistic. (a) P value = 0.0836 (b) P value = 0.4880 (c) P value < 0.0000 (d) P value = 0.0418 (e) P value = 0.9582 D. Find the critical value(s). D. __________ (a) z0 = –1.645 (b) z0 = 2.58 (c) z0 = 1.96 (d) z0 = 1.645 (e) t0 = –1.645 E. Based on your answers for parts A–D, what is your conclusion? (a) Do not reject H0 C. __________ (b) Reject H0 Copyright © Houghton Mifflin Company. All rights reserved. (c) Cannot determine E. __________ Instructor's Resource Guide Understandable Statistics, 9/e 148 CHAPTER 9 TEST FORM C PAGE 9 9. The average number of miles on vehicles traded in at Smith Brothers Motors is 64,000. Smith Brothers Motors has started a new deal offering lower financing charges. They are interested in whether the average mileage on trade-in vehicles has decreased. Test using = 0.01. The results (in thousands) from a random sample are listed below. Assume that mileage is normally distributed. 39 90 47 50 62 99 110 41 58 28 A. State the null and alternate hypotheses. 9. A. __________ (a) H0: x 62, 400; H1: x 62,400 (b) H0: x 64, 000; H1: x > 64,000 (c) H0: d = 64,000; H1: d < 64,000 (d) H0: = 64,000; H1: < 64,000 (e) H0: > 64,000; H1: > 64,000 B. Compute the z or t value of the sample test statistic. (a) t = –0.52 (b) t = –0.18 (c) t = –0.17 (d) t = –0.02 B. __________ (e) z = –0.58 C. Find the P value or an interval containing the P value for the sample test statistic. (a) Cannot determine (b) P value = 0.4286 (c) P value = 0.4325 (d) P value > 0.250 (e) 0.125 < P value < 0.250 D. Find the critical value(s). D. __________ (a) t0 = 2.821 (b) z0 = –2.33 (c) t0 = –2.821 (d) t0 = –3.250 (e) t0 = –2.764 E. Based on your answers for parts A–D, what is your conclusion? (a) Do not reject H0 C. __________ (b) Reject H0 E. __________ (c) Cannot determine Copyright © Houghton Mifflin Company. All rights reserved. Part III: Sample Chapter Tests and Answers CHAPTER 9 TEST 149 FORM C PAGE 10 10. Results from previous studies showed that 79% of all high-school seniors from a certain city plan to attend college after graduation. A random sample of 200 high-school seniors from this city showed that 162 plan to attend college. Does this indicate that the percentage has increased from that of previous studies? Test at 5% level of significance. A. State the null and alternate hypotheses. 10. A. __________ (a) H0: = 0.79; H1: > 0.79 (b) H0: p = 0.79; H1: p 0.79 (c) H0: p = 0.79; H1: p > 0.79 (d) H0: p̂ = 0.81; H1: p̂ 0.81 (e) H0: p̂ = 0.79; H1: p̂ > 0.79 B. Compute the z or t value of the sample test statistic. (a) z = 0.72 (b) t = 1.645 (c) z = 0.62 (d) z = 1.645 B. __________ (e) z = 0.69 C. Find the P value or an interval containing the P value for the sample test statistic. (a) P value = 0.2676 (b) P value = 0.7642 (c) P value < 0.05 (d) P value = 0.2451 (e) P value = 0.2358 D. Find the critical value(s). D. __________ (a) z0 = 1.645 (b) t0 = 2.33 (c) z0 = 2.33 (d) t0 = 2.58 (e) z0 = 1.96 E. Based on your answers for parts A–D, what is your conclusion? (a) Do not reject H0 C. __________ (b) Reject H0 Copyright © Houghton Mifflin Company. All rights reserved. (c) Cannot determine E. __________