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(22-18) A study was conducted to assess the effect of the drug imipramine on the treatment of patients with agoraphobia and panic disorder. The three treatment groups were a control, a low dose of 1.5 mg per kilogram of body weight, and a high dose of 3 mg per kilogram of body weight. There were 70 subjects, with 30 assigned at random to the control and 20 to each of the treatments. Subjects were classified as responders or nonresponders to treatment based on a battery of psychological tests. What is the number of degrees of freedom? mm Yes No A" 2 Control a n B. 3 15mm 9 ll C_ 6 Singlig 9 II D 70