11) Select the best choice for part A through D for full credit. Recall our live discussion on confidence intervals and see the textbook in Chapter 8.

a) The data below consists of the test scores of 32 students. Construct a 99% confidence interval for the population mean. 80 74 61 93 96 70 80 64 51 98 93 87 72 77 84 96 100 67 71 79 99 85 66 70 57 75 86 92 94 61 80 99

A) 70.7 < < 89.1 B) 73.6 < < 86.2 C) 75.3 < < 84.5 D) 72.2 < < 87.6

b) A survey of 865 voters in one state reveals that 408 favor approval of an issue before the legislature. Construct the 95% confidence interval for the true proportion of all voters in the state who favor approval.

A) 0.444 < p < 0.500 B) 0.438 < p < 0.505 C) 0.435 < p < 0.508 D) 0.471 < p < 0.472

c) A pollster wishes to estimate the true proportion of U.S. voters that oppose capital punishment. How many voters should be surveyed in order to be 92 percent confident that the true proportion is estimated to within 0.03?

A) 1 B) 851 C) 850 D) 26

d)The mean replacement time for a random sample of 20 washing machines is 9.0 years and the standard deviation is 2.2 years. Construct a 99% confidence interval for the standard deviation, , of the replacement times of all washing machines of this type.

A) 1.6 yr < < 4.6 yr B) 1.5 yr < < 4.2 yr C) 1.5 yr < < 3.7 yr D) 1.6 yr < < 3.5 yr