Everitt reported data on a study of three treatments for anorexia in young girls. One treatment was cognitive behaviour therapy, a second was a control condition with no therapy, and a third was a...

Everitt reported data on a study of three treatments for anorexia in young girls. One treatment was cognitive behaviour therapy, a second was a control condition with no therapy, and a third was a family therapy condition. The data follow:

a. Run an analysis of variance on group differences in Gain scores.

b. Repeat the analysis, but this time use a repeated measures design where the repeated measures are Pertest and Post-test.

c. How does the answer to part (b) relate to the answer to part (a)?

d. Plot scatterplots of the relationship between Pertest and Post-test separately for each group. What do these plots show?

e. Run a test on the null hypothesis that the Gain for the Control is 0.00. What does this analysis tell you? Are you surprised?

f. Why would significant gains in the two experimental groups not be interpretable without the control group?