14.11 Comparing therapies for anorexia The Anorexia data file on the book’s website shows weight change for 72 anorexic teenage girls who were randomly assigned to one of three psychological treatments (cognitive or family therapy and a control treatment). Use software to analyze these data. (The change scores are in the last three columns of the data set. Alternatively, the website also contains a dataset that shows the data in “long” format, with the treatment in one column and the change score in another column.)

a. Construct box plots for the three groups. Use these and sample summary means and standard deviations to describe the three samples.

b. For the one-way ANOVA comparing the three mean weight changes, report the test statistic and P-value.

Explain how to interpret.

c. State and check the assumptions for the test in part b.