07 TB Ch08

# We are interested in conducting a study in order to

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49. We are interested in conducting a study in order to determine what percentage of voters of a state would vote for the incumbent governor. What is the minimum size sample needed to estimate the pop- ulation proportion with a margin of error of 0.05 or less at 95% confidence? a. 200 b. 100 c. 58 d. 196 ANS: D PTS: 1 TOP: Interval Estimation

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50. In a sample of 400 voters, 360 indicated they favor the incumbent governor. The 95% confidence inter- val of voters not favoring the incumbent is NARRBEGIN: Exhibit 08-01 Exhibit 8-1 In order to estimate the average time spent on the computer terminals per student at a local university, data were collected for a sample of 81 business students over a one-week period. Assume the popula- tion standard deviation is 1.8 hours. NARREND 51. Refer to Exhibit 8-1. The standard error of the mean is 52. Refer to Exhibit 8-1. With a 0.95 probability, the margin of error is approximately 53. Refer to Exhibit 8-1. If the sample mean is 9 hours, then the 95% confidence interval is a. 7.04 to 110.96 hours b. 7.36 to 10.64 hours c. 7.80 to 10.20 hours d. 8.61 to 9.39 hours ANS: D PTS: 1 TOP: Interval Estimation NAR: Exhibit 08-01
NARRBEGIN: Exhibit 08-02 Exhibit 8-2 A random sample of 121 automobiles traveling on an interstate showed an average speed of 65 mph. From past information, it is known that the standard deviation of the population is 22 mph. NARREND 54. Refer to Exhibit 8-2. If we are interested in determining an interval estimate for at 96.6% confi- dence, the Z value to use is 55. Refer to Exhibit 8-2. The standard error of the mean is 56. Refer to Exhibit 8-2. If the confidence coefficient is reduced to 0.9, the standard error of the mean 57. Refer to Exhibit 8-2. The 96.6% confidence interval for is a. 63.00 to 67.00 b. 60.76 to 69.24 c. 61.08 to 68.92 d. 60.00 to 80.00 ANS: B PTS: 1 TOP: Interval Estimation

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NAR: Exhibit 08-02 58. Refer to Exhibit 8-2. If the sample size was 100 (other factors remain unchanged), the interval for would NARRBEGIN: Exhibit 08-03 Exhibit 8-3 The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took these 100 customers to check out was 3.0 minutes. It is known that the standard deviation of the population of checkout times is one minute. NARREND
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