# Question

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 to perform supervised volunteer work. During the sub-sequent five- year period, these same drivers were cited for the following number of moving violations:

NUMBER OF MOVING VIOLATIONS

TRAFFIC SCHOOL VOLUNTEER WORK

0.............. 26

0............... 7

15............. 4

9............... 1

7............... 1

0............. 14

2............... 6

23.............. 10

7

8

(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.

NUMBER OF MOVING VIOLATIONS

TRAFFIC SCHOOL VOLUNTEER WORK

0.............. 26

0............... 7

15............. 4

9............... 1

7............... 1

0............. 14

2............... 6

23.............. 10

7

8

(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.

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