126 Therapy for binge eaters. Do you experience episodes of excessive eating accompanied by being overweight? If so, you may suffer from binge eating disorder. Cognitivebehavioral therapy (CBT), in which patients are taught how to make changes in specific behavior patterns (e.g., exercise, eat only low-fat foods), can be effective in treating the disorder. A group of Stanford University researchers investigated the effectiveness of interpersonal therapy (IPT) as a second level of treatment for binge eaters ( Journal of Consulting and Clinical Psychology , June 1995). The researchers employed a design that randomly assigned a sample of 41 overweight individuals diagnosed with binge eating disorder to either a treatment group (30 subjects) or a control group (11 subjects). Subjects in the treatment group received 12 weeks of CBT and then were subdivided into two groups Those who responded successfully to CBT (17 subjects)

were assigned to a weight-loss therapy (WLT) program for the next 12 weeks. Those CBT subjects who did not respond to treatment (13 subjects) received 12 weeks of IPT. The subjects in the control group received no therapy of any type. Thus, the study ultimately consisted of three groups of overweight binge eaters: the CBTWLT group, the CBT-IPT group, and the control group.

One outcome (response) variable measured for each subject was the number x of binge eating episodes per week. Summary statistics for each of the three groups at the end of the 24-week period are shown in the accompanying table. The data were analyzed as a completely randomized design with three treatments (CBT-WLT, CBT-IPT, and Control). Although the ANOVA tables were not provided in the article, sufficient information is given in the table to reconstruct them. [See Exercise 38 .]

Is CBT effective in reducing the mean number of binges experienced per week?

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CBT-WLT CBT-IPT Control Sample size 17 13 11 Mean number of 0.2 1.9 2.9 binges per week Standard deviation 0.4 1.7 2.0 Based on Agras, W. S., et al. "Does interpersonal therapy help patients with binge cating disorder who fail to respond to cognitive-behavioral therapy?" Journal of Consulting and Clinical Psychology, Vol. 63, No. 3, June 1995, p. 358 (Table 1).