The procedures for the selection of a test population to use and evaluate the short units developed by the Sociological Resources for the Social Studies Project (SRSS), "Episodes in Social Inquiry Series," are considered. They wanted to assess the effectiveness of the materials under a variety of circumstances: classes from different parts of the country, from communities of various sizes and economic strata, with students of several ability levels, in a variety of social studies courses, in both large and small schools. Some of the problems discussed are: 1) school selection by geographical location; 2) working with the authority structure in public school systems; 3) deciding which contact in a school would be most receptive; 4) selecting the participant classes within a school; 5) soliciting the cooperation of the teachers; 6) establishing clear communications with the teachers about their role, the experimental nature of the episodes, and the desire for honest and candid feedback. The project concluded: when formative evaluation is the goal and time is an important factor, a test population selected on the basis of who will complete evaluation tasks is more important than a representative sampling of the total universe of potential users. ED 035 583 and SO 000 246 are related documents. (SBE)