ABSTRACT

The public investment analyst works with production functions supplied by technical experts. For example, for an agricultural project, the input-output data may come from agronomists and engineers, for a health project, from physicians, and for an educational project, from educational psychologists. Estimating project effects is usually referred to in the literature as evaluation research. Some differences in pre- and postproject observations may be caused by the passage of time. These differences would have occurred even without the project, for example, biological processes such as aging. The design of observations to determine whether a project made a difference involves timing of the observation relative to the initiation of the project and in comparison with other groups. Evaluations are subject to benefit-cost analysis as are other spending projects. The evaluation design that controls for more threats to validity probably costs more than a less powerful design.