Question

A school counselor in a high school would like to try out a new conflict-resolution program to reduce aggressiveness in students. She first surveyed 16 students using a 20-item instrument to measure their levels of aggression (on a scale of 0 to 10, with higher numbers meaning higher aggression levels). One month after the conflict resolution program was implemented, the students were given the same survey. The data are listed in the table below. The school counselor/researcher has set the significance level at α = .05.

	Aggressiveness rating
Subject	Before program	After program
1	6	4
2	2	3
3	3	1
4	5	5
5	7	7
6	4	4
7	2	3
8	4	3
9	2	1
10	8	3
11	3	3
12	5	4
13	5	4
14	8	4
15	6	7
16	1	4

4. Calculate the mean from the sample of the difference scores (2 points total: 1 for work, 1 for answer)

5. Estimate the standard deviation of the comparison population (that represents the null hypothesis) (2 points total: 1 for work, 1 for answer)

6. Calculate the standard error (standard deviation of the sampling distribution) (2 points total: 1 for work, 1 for answer)

7. Calculate the t statistic for the sample (2 points total: 1 for work, 1 for answer)

8. Because the hypotheses are directional, a one-tailed test can be performed. Determine the critical t value based on the degrees of freedom and the preset alpha level. (1 point)

Answer 1