The combined data for Exercises 18.10 and 18.12 are presented in the data file named Ex18.14.

I have added another variable named Group and coded it 1 and 2. This is a between-subject variable. Go to the website for the chapter and load Between1Within1.r. Run that and interpret the results.

Exercises 18.10

St. Lawrence, Brasfield, Shirley, Jefferson, Alleyne, and O’Brannon (1995) investigated the effects of an eight-week Behavioral Skills Training (BST) program aimed at reducing the risk of HIV infection among African-American adolescents. The study followed males and females from a pretest to a 12-month follow-up, recording the frequency of condom-protected sex.

(They also had a control condition, but I am going to look only at the males in the BST condition for this exercise.) The actual dependent variable is 1,000 times the natural logarithm of the frequency of protected sex. (I multiplied the log by 1,000 to eliminate decimal values.)

The data for males follow.

Exercises 18.12

In the study discussed in Exercise 18.10, the authors also ran a control group under the same conditions, but without the BST intervention. Those data (for males) follow.

Exercise 18.9

Calculate an estimate of d for the comparison you made in Exercise 18.8.

Exercise 18.8

Use the protected t tests with the data in Exercise 18.1 to help you interpret the results. However this time compare the mean of the two baseline measures with the mean of the three training measures.

Exercise 18.1

Migraine headaches are a problem for many people, and one way of treating them involves relaxation
therapy. A study of the effectiveness of relaxation techniques in the treatment of migraines
was conducted by Blanchard, Theobald, Williamson, Silver, and Brown (1978). The
data that follow are in agreement with those found by Blanchard et al. (Their study was more
complex than the one examined here.) I have calculated ΣX² to save you work.

Transcribed Image Text:

Pretest Posttest Follow-up Six Months Follow-up 12 Months 07 25 1306 22 13 17 14 24 10 50 36 49 23 38 34 33 25 24 10 07 13 33 22 23 27 22 20 21 04 00 17 16 22 12 20 222222=82 24 25 26 24 00 10