File: Ch08, Chapter 8: Statistical Inference: Estimation for Single Populations

True/False

1. When a statistic calculated from sample data is used to estimate a population parameter, it is called a point estimate.

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Easy

2. When a range of values is used to estimate a population parameter, it is called a range estimate.

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Easy

3. If the population is not normal but its standard deviation, s is known and the sample size, n is large (n ≥ 30), z-distribution values may be used to determine interval estimates for the population mean.

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

4. If the population is normal and its standard deviation, s, is known but the sample size is small, z-distribution values may not be used to determine interval estimates for the population mean.

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

5. When the population standard deviation, s, is unknown the sample standard deviation, s, is used in determining the interval estimate for the population mean.

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Medium

6. If the population is normal and its standard deviation, s, is known and the sample size, n, is large (n ≥ 30), interval estimates for the population mean must be determined using z-values.

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)Difficulty: Medium

7. An assumption underlying the use of t-statistic in sample-based estimation is that the population is normally distributed.

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Medium

8. A t-distribution is similar to a normal distribution, but with flatter tails.

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Easy

9. In order to find values in the t distribution table, you must determine the appropriate degrees of freedom based on the sample sizes. 

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Easy

10. If the degrees of freedom in a t distribution increase, difference between the t values and the z values will also increase.

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Medium

11. In determining the interval estimates for a population proportion using the sample proportion, it is appropriate to use the values from a t-distribution rather than the z-distribution.

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

12. In determining the interval estimates for a population variance using the sample variance, it is appropriate to use the values from a chi-square distribution rather than a t-distribution.

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

13. In estimating the sample size necessary to estimate a population mean, the error of estimation, E, is equal to the difference between the sample mean and the population mean

Ans:

Response: See section 8.5 Estimating the Sample Variance

Difficulty: Medium

14. Use of the chi-square statistic to estimate the population variance is extremely robust to the assumption that the population is normally distributed.

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

15. Like a t-distribution, a chi-square distribution is symmetrical and extends from minus infinity to plus infinity.

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

Multiple Choice

16. Catherine Chao, Director of Marketing Research, is evaluating consumer acceptance of a new toothpaste package.  Her staff reports that 17% of a random sample of 200 households prefers the new package to all other package designs.  If Catherine concludes that 17% of all households prefer the new package, she is using a _______.

a) a point estimate

b) a range estimate

c) a statistical parameter

d) an interval estimate

e) an exact estimate

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

17. Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers. Accordingly, his staff recorded the waiting times for 45 randomly selected walk-in customers, and calculated that their mean waiting time was 15 minutes. If Brian concludes that the average waiting time for all walk-in customers is 15 minutes, he is using a ________.

a) a range estimate

b) a statistical parameter

c) an interval estimate

d) a point estimate

e) an exact estimate

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

18. Eugene Gates, Marketing Director of Mansfield Motors Manufacturers, Inc.’s Electrical Division, is leading a study to assess the relative importance of product features. An item on a survey questionnaire distributed to 100 of Mansfield’s customers asked them to rate the importance of “ease of maintenance” on a scale of 1 to 10 (with 1 meaning “not important” and 10 meaning “highly important”). His staff assembled the following statistics.

Ease of Maintenance

Mean

7.5

Standard Deviation

1.5

If Eugene concludes that the average rate of “ease of maintenance” for all customers is 7.5, he is using ________.

a) a range estimate

b) a statistical parameter

c) a point estimate

d) an interval estimate

e) a guesstimate

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

19. The z value associated with a two‑sided 90% confidence interval is _______.

a) 1.28

b) 1.645

c) 1.96

d) 2.575

e) 2.33

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

20. The z value associated with a two‑sided 95% confidence interval is _______.

a) 1.28

b) 1.645

c) 1.96

d) 2.575

e) 2.33

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

21. The z value associated with a two‑sided 80% confidence interval is _______.

a) 1.645

b) 1.28

c) 0.84

d) 0.29

e) 2.00

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

22. The z value associated with a two‑sided 88% confidence interval is _______.

a) 1.28

b) 1.55

c) 1.17

d) 0.88

e) 1.90

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

23. Suppose a random sample of 36 is selected from a population with a standard deviation of 12. If the sample mean is 98, the 99% confidence interval to estimate the population mean is _______.

a) 94.08 to 101.92

b) 92.85 to 103.15

c) 97.35 to 98.65

d) 93.34 to 102.66

e) 90.20 to 105.00

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

24. Suppose a random sample of 36 is selected from a population with a standard deviation of 12. If the sample mean is 98, the 90% confidence interval for the population mean is _______.

a) 94.71 to 101.29

b) 97.45 to 98.55

c) 94.08 to 101.92

d) 97.35 to 98.65

e) 95.00 to 105.00

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

25. Suppose a random sample of size 64 is selected from a population yielding a sample mean of 26.  The population standard deviation is 4. From this information, the 90% confidence interval to estimate the population mean can be computed to be _______.

a) 25.36 to 26.64

b) 25.92 to 26.08

c) 25.18 to 26.82

d) 25.90 to 26.10

e) 26.00 to 27.80

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

26. Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers.  Accordingly, his staff recorded the waiting times for 64 randomly selected walk-in customers and determined that their mean waiting time was 15 minutes.  Assume that the population standard deviation is 4 minutes.  The 90% confidence interval for the population mean of waiting times is ________.

a) 14.27 to 15.73

b) 14.18 to 15.82

c) 9.88 to 20.12

d) 13.86 to 16.14

e) 18.12 to 19.87

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

27. Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers.  Accordingly, his staff recorded the waiting times for 64 randomly selected walk-in customers and determined that their mean waiting time was 15 minutes.  Assume that the population standard deviation is 4 minutes.  The 95% confidence interval for the population mean of waiting times is ________.

a) 14.02 to 15.98

b) 7.16 to 22.84

c) 14.06 to 15.94

d) 8.42 to 21.58

e) 19.80 to 23.65

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

28. James Desreumaux, VP of Human Resources of American First Banks (AFB), is reviewing the employee training programs of AFB banks.  His staff randomly selected personnel files for 100 tellers in the Southeast Region and determined that their mean training time was 25 hours.  Assume that the population standard deviation is 5 hours.  The 88% confidence interval for the population mean of training times is ________.

a) 17.25 to 32.75

b) 24.23 to 25.78

c) 24.42 to 25.59

d) 19.15 to 30.85

e) 21.00 t0 32.00

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

29. James Desreumaux, VP of Human Resources of American First Banks (AFB), is reviewing the employee training programs of AFB banks.  His staff randomly selected personnel files for 100 tellers in the Southeast Region and determined that their mean training time was 25 hours.  Assume that the population standard deviation is 5 hours.  The 92% confidence interval for the population mean of training times is ________.

a) 16.25 to 33.75

b) 24.30 to 25.71

c) 17.95 to 32.05

d) 24.12 to 25.88

e) 24.45 to 27.32

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

30. James Desreumaux, VP of Human Resources of American First Banks (AFB), is reviewing the employee training programs of AFB banks.  His staff randomly selected personnel files for 100 tellers in the Southeast Region and determined that their mean training time was 25 hours.  Assume that the population standard deviation is 5 hours.  The 95% confidence interval for the population mean of training times is ________.

a) 15.20 to 34.80

b) 24.18 to 25.82

c) 24.02 to 25.98

d) 16.78 to 33.23

e) 23.32 to 35.46

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

31. A random sample of 64 items is selected from a population of 400 items. The sample mean is 200.  The population standard deviation is 48. From this data, a 95% confidence interval to estimate the population mean can be computed as _______.

a) 189.21 to 210.79

b) 188.24 to 211.76

c) 190.13 to 209.87

d) 190.94 to 209.06

e) 193.45 to 211.09

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

32. A random sample of 64 items is selected from a population of 400 items. The sample mean is 200.  The population standard deviation is 48. From this data, a 90% confidence interval to estimate the population mean can be computed as _______.

a) 189.21 to 210.79

b) 188.24 to 211.76

c) 190.13 to 209.87

d) 190.94 to 209.06

e) 193.45 to 211.09

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

33. The normal distribution is used to test about a population mean for large samples if the population standard deviation is known.  “Large” is usually defined as _______.

a) at least 10

b) at least 5% of the population size

c) at least 30

d) at least 12

e) at least 100

Ans:

Response: See section 8.1 Estimating the Population Mean using the z Statistic (s Known)

Difficulty: Medium

34. The table t value associated with the upper 5% of the t distribution and 12 degrees of freedom is _______.

a) 2.179

b) 1.782

c) 1.356

d) 3.055

e) 3.330

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Easy

35. The table t value associated with the upper 5% of the t distribution and 14 degrees of freedom is _______.

a) 2.977

b) 2.624

c) 2.145

d) 1.761

e)

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (sUnknown)

Difficulty: Easy

36. The table t value associated with the upper 10% of the t distribution and 23 degrees of freedom is _______.

a) 1.319

b) 1.714

c) 2.069

d) 1.321

e) 2.332

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Easy

37. A researcher is interested in estimating the mean value for a population. She takes a random sample of 17 items and computes a sample mean of 224 and a sample standard deviation of 32. She decides to construct a 98% confidence interval to estimate the mean. The degrees of freedom associated with this problem are _______.

a) 18

b) 17

c) 16

d) 15

e) 20

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Easy

38. The lengths of steel rods produced by a shearing process are normally distributed.  A random sample of 10 rods is selected; the sample mean length is 119.05 inches; and the sample standard deviation is 0.10 inch.  The 95% confidence interval for the population mean rod length is ______________.

a) 118.99 to 119.11

b) 118.82 to 119.28

c) 118.98 to 119.12

d) 118.85 to 119.25

e) 119.89 to 122.12

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Medium

39. The lengths of steel rods produced by a shearing process are normally distributed.  A random sample of 10 rods is selected; the sample mean length is 119.05 inches; and the sample standard deviation is 0.10 inch.  The 90% confidence interval for the population mean rod length is ______________.

a) 118.99 to 119.11

b) 118.87 to 119.23

c) 119.00 to 119.10

d) 118.89 to 119.21

e) 119.21 to 123.87

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Medium

40. The weights of aluminum castings produced by a process are normally distributed.  A random sample of 5 castings is selected; the sample mean weight is 2.21 pounds; and the sample standard deviation is 0.12 pound.  The 98% confidence interval for the population mean casting weight is _________.

a) 1.76 to 2.66

b) 2.01 to 2.41

c) 2.08 to 2.34

d) 1.93 to 2.49

e) 2.49 to 2.67

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Medium

41. Life tests performed on a sample of 13 batteries of a new model indicated:  (1) an average life of 75 months, and (2) a standard deviation of 5 months.  Other battery models, produced by similar processes, have normally distributed life spans.  The 98% confidence interval for the population mean life of the new model is _________.

a) 63.37 to 86.63

b) 61.60 to 88.41

c) 71.77 to 78.23

d) 71.28 to 78.72

e) 79.86 to 81.28

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (s Unknown)

Difficulty: Medium

42. Life tests performed on a sample of 13 batteries of a new model indicated:  (1) an average life of 75 months, and (2) a standard deviation of 5 months. Other battery models, produced by similar processes, have normally distributed life spans. The 90% confidence interval for the population mean life of the new model is _________.

a) 66.78 to 83.23

b) 72.72 to 77.28

c) 72.53 to 77.47

d) 66.09 to 83.91

e) 73.34 to 76.25

Ans:

Response: See section 8.2 Estimating the Population Mean using the t Statistic (sUnknown)

Difficulty: Medium

43. A researcher wants to estimate the proportion of the population which possesses a given characteristic. A random sample of size 800 is taken resulting in 360 items which possess the characteristic. The point estimate for this population proportion is _______.

a) 0.55

b) 0.45

c) 0.35

d) 0.65

e) 0.70

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

44. A researcher wants to estimate the proportion of the population which possesses a given characteristic. A random sample of size 1800 is taken resulting in 450 items which possess the characteristic. The point estimate for this population proportion is _______.

a) 0.55

b) 0.45

c) 0.35

d) 0.25

e) 0.15

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

45. A researcher wants to estimate the proportion of a population which possesses a given characteristic. A random sample of size 250 is taken and 40% of the sample possesses the characteristic. The 90% confidence interval to estimate the population proportion is ____.

a) 0.35 to 0.45

b) 0.34 to 0.46

c) 0.37 to 0.43

d) 0.39 to 0.41

e) 0.40 to 0.45

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

46. A researcher wants to estimate the proportion of a population which possesses a given characteristic. A random sample of size 250 is taken and 40% of the sample possesses the characteristic. The 95% confidence interval to estimate the population proportion is _______.

a) 0.35 to 0.45

b) 0.34 to 0.46

c) 0.37 to 0.43

d) 0.39 to 0.41

e) 0.40 to 0.42

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

47. A researcher wants to estimate the proportion of a population which possesses a given characteristic. A random sample of size 200 is taken and 30% of the sample possesses the characteristic. The 95% confidence interval to estimate the population proportion is _______.

a) 0.53 to 0.67

b) 0.25 to 0.35

c) 0.24 to 0.36

d) 0.27 to 0.33

e) 0.28 to 0.34

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

48. A researcher wants to estimate the proportion of a population which possesses a given characteristic. A random sample of size 200 is taken and 30% of the sample possesses the characteristic. The 90% confidence interval to estimate the population proportion is _______.

a) 0.53 to 0.67

b) 0.25 to 0.35

c) 0.24 to 0.36

d) 0.27 to 0.33

e) 0.33 to 0.39

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

49. A random sample of 225 items from a population results in 60% possessing a given characteristic. Using this information, the researcher constructs a 99% confidence interval to estimate the population proportion. The resulting confidence interval is _______.

a) 0.54 to 0.66

b) 0.59 to 0.61

c) 0.57 to 0.63

d) 0.52 to 0.68

e) 0.68 to 0.76

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

50. A random sample of 225 items from a population results in 60% possessing a given characteristic. Using this information, the researcher constructs a 90% confidence interval to estimate the population proportion. The resulting confidence interval is _______.

a) 0.546 to 0.654

b) 0.536 to 0.664

c) 0.596 to 0.604

d) 0.571 to 0.629

e) 0.629 to 0.687

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

51. Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS e-mail for non-business communications.  A random sample of 200 e-mail messages was selected.  Thirty of the messages were not business related. The point estimate for this population proportion is _______.

a) 0.150

b) 0.300

c) 0.182

d) 0.667

e) 0.786

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

52. Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS e-mail for non-business communications.  A random sample of 200 e-mail messages was selected.  Thirty of the messages were not business related. The 90% confidence interval for the population proportion is _________.

a) 0.108 to 0.192

b) 0.153 to 0.247

c) 0.091 to 0.209

d) 0.145 to 0.255

e) 0.255 to 0.265

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

53. Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS e-mail for non-business communications.  A random sample of 200 e-mail messages was selected.  Thirty of the messages were not business related. The 95% confidence interval for the population proportion is _________.

a) 0.108 to 0.192

b) 0.153 to 0.247

c) 0.091 to 0.209

d) 0.101 to 0.199

e) 0.199 to 0.201

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

54. Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS e-mail for non-business communications.  A random sample of 200 e-mail messages was selected.  Thirty of the messages were not business related. The 98% confidence interval for the population proportion is _________.

a) 0.108 to 0.192

b) 0.153 to 0.247

c) 0.091 to 0.209

d) 0.145 to 0.255

e) 0.250 to 0.275

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

55. Catherine Chao, Director of Marketing Research, is evaluating consumer acceptance of a new toothpaste package.  She randomly selects a sample of 200 households.  Forty households prefer the new package to all other package designs.  The point estimate for this population proportion is _______.

a) 0.20

b) 0.25

c) 0.40

d) 0.45

e) 0.55

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

56. Catherine Chao, Director of Marketing Research, is evaluating consumer acceptance of a new toothpaste package.  She randomly selects a sample of 200 households.  Forty households prefer the new package to all other package designs.  The 90% confidence interval for the population proportion is _________.

a) 0.199 to 0.201

b) 0.153 to 0.247

c) 0.164 to 0.236

d) 0.145 to 0.255

e) 0.185 to 0.275

Ans:

Response: See section 8.3 Estimating the Population Proportion

Difficulty: Medium

57. Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers.  Brian would like to minimize the variance of waiting time for these customers, since this would mean each customer received the same level of service.  Accordingly, his staff recorded the waiting times for 15 randomly selected walk-in customers, and determined that their mean waiting time was 15 minutes and that the standard deviation was 4 minutes.  Assume that waiting time is normally distributed.  The 90% confidence interval for the population variance of waiting times is ________.

a) 9.46 to 34.09

b) 56.25 to 64.87

c) 11.05 to 16.03

d) 8.58 to 39.79

e) 12.50 to 42.35

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

58. Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers.  Brian would like to minimize the variance of waiting time for these customers, since this would mean each customer received the same level of service.  Accordingly, his staff recorded the waiting times for 15 randomly selected walk-in customers, and determined that their mean waiting time was 15 minutes and that the standard deviation was 4 minutes.  Assume that waiting time is normally distributed.  The 95% confidence interval for the population variance of waiting times is ________.

a) 9.46 to 34.09

b) 56.25 to 64.87

c) 11.05 to 16.03

d) 8.58 to 39.79

e) 12.50 to 42.35

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

59. Velma Vasquez, fund manager of the Vasquez Value Fund, manages a portfolio of 250 common stocks.  Velma relies on various statistics, such as variance, to assess the overall risk of stocks in an economic sector. Her staff reported that for a sample 14 utility stocks the mean annualized return was 14% and that the variance was 3%.  Assume that annualized returns are normally distributed.  The 90% confidence interval for the population variance of annualized returns is _______.

a) 0.018 to 0.064

b) 0.016 to 0.078

c) 0.017 to 0.066

d) 0.016 to 0.075

e) 0.020 to 0.080

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

60. Velma Vasquez, fund manager of the Vasquez Value Fund, manages a portfolio of 250 common stocks.  Velma relies on various statistics, such as variance, to assess the overall risk of stocks in an economic sector. Her staff reported that for a sample 14 utility stocks the mean annualized return was 14% and that the variance was 3%.  Assume that annualized returns are normally distributed.  The 95% confidence interval for the population variance of annualized returns is _______.

a) 0.018 to 0.064

b) 0.016 to 0.078

c) 0.017 to 0.066

d) 0.016 to 0.075

e) 0.020 to 0.080

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

61. James Desreumaux, VP of Human Resources of American First Banks (AFB), is reviewing the employee training programs of AFB banks.  His staff randomly selected personnel files for 10 tellers in the Southwest Region, and determined that their mean training time was 25 hours and that the standard deviation was 5 hours.  Assume that training times are normally distributed.  The 90% confidence interval for the population variance of training times is ________.

a) 11.83 to 83.33

b) 2.37 to 16.67

c) 2.66 to 13.51

d) 13.30 to 67.57

e) 15.00 to 68.00

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

62. James Desreumaux, VP of Human Resources of American First Banks (AFB), is reviewing the employee training programs of AFB banks.  His staff randomly selected personnel files for 10 tellers in the Southwest Region, and determined that their mean training time was 25 hours and that the standard deviation was 5 hours.  Assume that training times are normally distributed.  The 95% confidence interval for the population variance of training times is ________.

a) 11.83 to 83.33

b) 2.37 to 16.67

c) 2.66 to 13.51

d) 13.30 to 67.57

e) 15.40 to 68.28

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

63. Given n = 17, s2 = 18.56, and that the population is normally distributed, the 80% confidence interval for the population variance is ________.

a) 11.4372 £ s 2 £ 36.3848

b) 23.5418 £ s 2 £ 9.31223

c) 12.6141 £ s 2 £ 31.8892

d) 11.2929 £ s 2 £ 37.2989

e) 14.2929 £ s 2 £ 39.2989

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

64. Given n = 12, s2 = 44.90, and that the population is normally distributed, the 99% confidence interval for the population variance is ________.

a) 19.0391 £ s 2 £ 175.2888

b) 23.0881 £ s 2 £ 122.3495

c) 25.6253 £ s 2 £ 103.0993

d) 18.4588 £ s 2 £ 189.7279

e) 14.2929 £ s 2 £ 139.2989

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

65. Given n = 20, s = 32, and that the population is normally distributed, the 90% confidence interval for the population variance is ________.

a) 645.4458 £ s 2 £ 1923.0986

b) 599.3635 £ s 2 £ 2135.3859

c) 592.2258  £ s 2 £  2184.4685

d) 652.0129 £ s 2 £ 1887.4185

e) 642.0929 £ s 2 £ 3982.2989

Ans:

Response: See section 8.4 Estimating the Population Variance

Difficulty: Medium

66. A researcher wants to determine the sample size necessary to adequately conduct a study to estimate the population mean to within 5 points. The range of population values is 80 and the researcher plans to use a 90% level of confidence. The sample size should