where n = number of subjects needed in each group p1 = percentage of patients in the control group who were not re-hospitalized q1 = percentage of patients in the control group who were re-hospitalized p2 = percentage of patients in the intervention group who were not re-hospitalized q2 = percentage of patients in the control group who were re-hospitalized f(alpha,beta) = 7.9 when alpha = .05 (two-sided) and beta = .20