This booklet contains questions and answers about random assignment in program evaluation and intervention research. The main purpose of program evaluation research in education is to determine whether programs help the students they are designed to serve and whether new ideas for education programs still under development are worthy of extension to a wider selection of schools and settings. Researchers use random assignment in impact studies to form two statistically equivalent groups of participants in the most objective way possible. Random assignment procedures vary according to the program being tested. The main advantage of using random assignment is a "one-difference-only" feature to help determine whether changes are the result of the intervention or program. Other approaches can be used to study the effects of a new program, but random assignment is the best approach for discerning whether or not a new school policy or program has an effect over and above the effect of the standard policy or program and how big that effect might be. (SLD)