6.25 In a small pilot study, a psychiatrist wanted to examine the effects of the drug lithium on bulimics (bulimics have continuous abnormal hunger and frequently go on eating binges). Although evidence of the effectiveness of lithium on bulimics has been shown, he was not sure if depressed subjects would respond differently than those without depression. He treated eight teenage female patients with lithium for 12 weeks; four of the subjects were diagnosed with depression, and half of the subjects received behavioral therapy. At the end of each four-week period, he recorded the number of binges each subject had during that week. The following are the results:

Fit a longitudinal model that addresses the concerns of the psychiatrist.
Because the data are counts (number of occurrences), consider a square root transformation prior to the analysis.

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Weekly Number of Binges Subject Depression Week 0 Week 4 Week 8 Week 12 1 No 13 23456780 No 15 No 16 No 14 Yes 10 Yes 18 Yes 16 Yes 19 223447 BB4255 34427768 0 0 1 1