Researchers wanted to test the effectiveness of a new cognitive behavioral therapy (CBT) compared with both an older behavioral treatment and a placebo therapy for treating insomnia. They identified 150 adults with insomnia. Patients were randomly assigned to one of three treatment groups. Fifty patients were randomly assigned to receive CBT (sleep education, stimulus control, and time-in-bed restrictions), another 50 received muscle relaxation training (RT), and the final 50 received a placebo treatment. Treatment lasted 6 weeks, with follow-up conducted at 6 months. To measure the effectiveness of the treatment, researchers used wake time after sleep onset (WASO). CBT produced larger improvements than did RT or placebo treatment. For example, the CBT-treated patients achieved an average 56% reduction in their WASO, whereas RT-treated and placebo-treated patients, respectively, achieved only 14% and 13% reductions in this measure. Results suggest that CBT treatment leads to significant sleep improvements within 6 weeks, and these improvements appear to endure through 6 months of follow-up.
what is the response variable