Review Q. 20.5

20.5 A group of high-risk automobile drivers (with three moving violations in one year) are required, according to random assignment, either to attend a traffic school or toperform supervised volunteer work. During the subsequent five-year period, thesesame drivers were cited for the following number of moving violations:

NUMBER OF MOVING VIOLATIONSTRAFFIC SCHOOLVOLUNTEER WORK 02607154917101426231078 (a) Why might the Mann-Whitney U test be preferred to the t test for these data? (b) Use U to test the null hypothesis at the .05 level of significance (c) Specify the approximate p-value for this test result.

20.6 A social psychologist wishes to test the assertion that our attitude toward other peo-ple tends to reflect our perception of their attitude toward us. A randomly selectedmember of each of 12 couples who live together is told (in private) that his or her partner has rated that person at the high end of a 0 to 100 scale of trustworthi-ness. The other member is told (also in private) that his or her partner has rated that person at the low end of the trustworthiness scale. Each person is then asked to estimate, in turn, the trustworthiness of his or her partner, yielding the following results. (According to the original assertion, the people in the trustworthy condition should give higher ratings than should their partners in the untrustworthy condition.)TRUSTWORTHINESS RATINGSCOUPLETRUSTWORTHY (1)UNTRUSTWORTHY (2)A7560B3530C5055D9320E7412F4734G9522H6363I4443J8879K5633L8672 (a) Use T to test the null hypothesis at the .01 level. (b) Specify the approximate p-value for this test

20.7 Does background music influence the scores of college students on a reading comprehension test? Sets of 10 randomly selected students take a reading comprehension test with rock, country-western, or classical music in the back-ground. The results are as follows (higher scores reflect better comprehension)READING COMPREHENSION SCORESROCK (1)COUNTRY-WESTERN (2)CLASSICAL (3)9099521194758295916723949872979381317379839028858794100847769 (a) Why might the H test be preferred to the F test for these data? (b) Use H to test the null hypothesis at the .05 level of significance