14.20 Four different experimental methods of treating schizophrenia,

(1) weekly shock treatments, (2) weekly treatments of carbon dioxide inhalations, (3) biweekly shock treatment alternated with biweekly carbon dioxide inhalations, and (4) tranquilizer drug treatment, are compared by assigning a group of schizophrenic patients randomly into four treatment groups. The data below are the number of patients who did and did not improve in 4 weeks of treatment. Test the null hypothesis that the treatments are equally effective.

Treatment Number Improved Number not Improved 1 43 12 2 24 28 3 32 16 4 29 24