A. 912 ± 49.2
B. 912 ± 42.6
C. 912 ± 44.3
D. 912 ± 46.8
2. The number of beverage cans produced each hour from a vending machine is normally distributed with a standard deviation of 8.6. For a random sample of 12 hours, the average number of beverage cans produced was 326.0. Assume a 99% confidence interval for the population mean number of beverage cans produced per hour. Calculate the margin of error of the 99% confidence interval.
A. 1.85
B. 3.60
C. 6.41
D. 10.56
3. The number of beverage cans produced each hour from a vending machine is normally distributed with a standard deviation of 8.6. For a random sample of 12 hours, the average number of beverage cans produced was 326.0. Assume a 99% confidence interval for the population mean number of beverage cans produced per hour. Find the upper confidence limit of the 99% confidence interval.
A. 340.25
B. 325.98
C. 319.59
D. 332.41
4. If we change a 95% confidence interval estimate to a 99% confidence interval estimate, we can expect
A. the size of the confidence interval to increase
B. the size of the confidence interval to decrease
C. the size of the confidence interval to remain the same
D. the sample size to increase
Midterm 2 – Practice Exercises
2
5. If a sample has 20 observations and a 90% confidence estimate for µ is needed, the appropriate t‐score is:
A. 2.120
B. 1.746
C. 2.131
D. 1.729
6. We are interested in conducting a study to determine what percentage of voters would vote for the incumbent member of parliament. What is the minimum size sample needed to estimate the population proportion with a margin of error of 0.07 or less at 95% confidence?
A. 200
B. 100
C. 58
D. 196
7. The sample size needed to provide a margin of error of 2 or less with a 0.95 confidence coefficient when the population standard deviation equals 11 is
A. 10
B. 11
C. 116
D. 117
8. The manager of the local health club is interested in determining the number of times members use the weight room per month. She takes a random sample of 15 members and finds that over the course of a month, the average number of visits was 11.2 with a standard deviation of 3.2. Assuming that the monthly number of visits is normally distributed, which of the following represents a 95% confidence
interval for the average monthly usage of all health club members?
A. 11.2 ± 1.74
B. 11.2 ± 1.77
C. 11.2 ± 1.62
D. 11.2 ± 1.83
Midterm 2 – Practice Exercises
3
9. The supervisor of a production line believes that the average time to assemble an electronic component is 14 minutes. Assume that assembly time is normally distributed with a standard deviation of 3.4 minutes. The supervisor times the assembly of 14 components, and finds that the average time for completion is 11.6 minutes. What are the appropriate null and alternative hypotheses?
A. H0 : µ ≥ 14 and H1: µ < 14
B. H0 : µ ≤ 14 and H1: µ > 14
C. H0 : µ = 14 and H1: µ ≠ 14
D. H0 : µ ≠ 14 and H1: µ = 14
10. The supervisor of a production line believes that the average time to assemble an electronic component is 14 minutes. Assume that assembly time is normally distributed with a standard deviation of 3.4 minutes. The supervisor times the assembly of 14 components, and finds that the average time for completion is 11.6 minutes. What are the appropriate null and alternative hypotheses? Which of the following statements is most accurate?
A. fail to reject the null hypothesis at α ≤ 0.10
B. reject the null hypothesis at α = 0.025, but not at α = 0.05
C. reject the null hypothesis at α = 0.05, but not at α = 0.01
D. reject the null hypothesis at α = 0.01
11. For a one-tailed hypothesis test (upper tail) the p-value is computed to be 0.034. If the test is being conducted at 95% confidence, the null hypothesis
A. could be rejected or not rejected depending on the sample size
B. could be rejected or not rejected depending on the value of the mean of the
sample
C. is not rejected
D. is rejected
12. In a two-tailed hypothesis test the test statistic z is determined to be –2.5. The pvalue for this test is
A. −1.25
B. 0.4938
C. 0.0062
D. 0.0124
13. An accountant claims to be able to complete a standard tax return in under an hour. For a random sample of 24 tax returns, the accountant averaged 63.2 minutes with a standard deviation of 7.7 minutes. What is the test statistic for this test?
A. Z = 2.04
B. t = 1.79
C. t = 2.04
D. Z = 1.79
14. An accountant claims to be able to complete a standard tax return in under an hour. For a random sample of 24 tax returns, the accountant averaged 63.2 minutes with a standard deviation of 7.7 minutes. What are the appropriate null and alternative hypotheses?
A. H0 : µ = 60 and H1 : µ ≠ 60
B. H0 : µ = 60 and H1 : µ > 60
C. H0 : µ = 60 and H1 : µ < 60
D. H0 : µ > 60 and H1 : µ ≤ 60
15. An accountant claims to be able to complete a standard tax return in under an hour. For a random sample of 24 tax returns, the accountant averaged 63.2 minutes with a standard deviation of 7.7 minutes. What is the most accurate estimate of the p‐value?
A. 0.025 < p‐value < 0.05
B. 0.01 < p‐value < 0.025
C. 0.05 < p‐value < 0.10
D. p‐value < 0.01
16. Salary information regarding male and female employees of a large company is shown
Male Female
Sample Size (n) 64 36
Sample Mean Salary (in 1,000) 44 41
Population Variance (σ2 ) 128 72
We want to test whether the mean salary of female (µF) is bigger than mean salary of male (µM). What are the appropriate null and the alternative hypotheses?
A. H0: µF = µM , HA: µF ≠ µM
B. H0: µF > µM , HA: µF ≤ µM
C. H0: µF < µM , HA: µF ≥ µM
D. H0: µF= µM , HA: µF>µM
17. Salary information regarding male and female employees of a large company is shown
Male Female
Sample Size (n) 64 36
Sample Mean Salary (in 1,000) 44 41
Population Variance (σ2
) 128 72
We want to test whether the mean salary of female (µF) is bigger than mean salary of male (µM). What is the test statistic?
A. 1.75
B. 2.0
C. 1.5
D. 1.25
18. Test scores on a standardized test from samples of students from two universities are given below.
A B
Sample size 28 41
Average test score 84 82
Variance 64 100
90% confidence interval estimate for the difference between the test scores of the two universities:
A. 0.72 to 4.94
B. -1.63 to 5.63
C. -2.91 to 3.55
D. -0.88 to 6.17
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