Evaluation of Family Preservation and Reunification Programs: Interim Report. 1.2.2 Sample Size


Each site was evaluated separately. To detect a difference of 15 percentage points between the experimental and control groups in such characteristics as placement rates with a probability of .8, we set a goal of 500 cases in each site, about 250 in each group. Even with this sample size, our ability to detect small differences is limited. Initially we hoped to enroll 500 families in each site over a one-year period. However, the sample accumulation in sites in this report, Kentucky, New Jersey, and Tennessee was slower than expected. A 349-case sample size was achieved in Kentucky after enrolling families for two years. In New Jersey, 442 net cases were enrolled over an 18-month period and in Tennessee, 147 net cases were enrolled over a 21-month period.