A)

A simple random sample of frontseat occupants involved in car crashes is obtained. Among 2715 occupants not wearing seat belts, 39 were killed. Among 7768 occupants wearing seat belts, 20 were killed. Use a 0.01 significance level to test the claim that seat belts are effective in reducing fatalities. Complete parts (a) through (0) below. (3 Consider the rst sample to be the sample of occupants not wearing seat belts and the second sample to be the sample of occupants wearing seat belts. What are the null and alternative hypotheses for the hypothesis test? a'jz- A. H0: p1 =p2 {fir B. H0: p1 5p2 {:12- 0. H0: p1 2p2 H15P192 H1ip1P2 \"1:91:92 A study was done on proctored and nonproctored tests. The results are shown in the table. Assume that the two ProctoredNonproctored samples are independent simple random samples selected from normally distributed populations. and do not assume that the population standard deviations are equal. Complete parts (a) and (b) below. EH 3 \fListed below are time intervals (min) between eruptions of a geyser. Assume that the "recent" times are within the past few years, the "past" times are from around 20 years ago, and that the two samples are independent simple random samples selected from normally distributed populations. Do not assume that the population standard deviations are equal. Does it appear that the mean time interval has changed? Is the conclusion affected by whether the significance level is 0.10 or 0.01? Recent 79 92 88 80 57 99 63 88 70 88 82 82 57 81 75 102 61 D Past 89 88 93 94 65 85 85 92 88 91 89 91 Let p, be the recent times and let 2 be the past times. What are the null and alternative hypotheses? OB. Ho: My = H2 OA. Ho: My # 12 H: My # H2 H: H1 = H2 OD. Ho: My = H2 OC. Ho: My

H 2 H: H1 = H2