They are not necessarily reliable or valid for specific programs. If not, then a local item analysis and perhaps test recalibration is needed. In lieu of control-comparison group hypothesis testing, we advocate the use of case studies, the computation of effect sizes, and the examination of growth curves. Case studies can provide rich data to help policy makers and researchers understand interventions. Effect sizes help gauge the relative contributions of the intervention.
Growth curves can help identify trends and control for some error.
The effects of the Head Start Program on children's cognitive development. Applegate, B . Bayley, N . Bayley, N . From affect to empirical effect.