This article reviews the origins and use of the terms quasi-experiment and natural experiment. It demonstrates how the terms conflate whether variation in the independent variable of interest falls short of random with whether researchers find, rather than intervene to create, that variation. Using the lens of assignment--the process driving…

Researchers have become increasingly interested in programs' main and interaction effects of two variables (A and B, e.g., two treatment variables or one treatment variable and one moderator) on outcomes. A challenge for estimating main and interaction effects is to eliminate selection bias across A-by-B groups. I introduce Rubin's causal model to…

Sound evaluation planning requires numerous decisions about how constructs in a program theory will be translated into measures and instruments that produce evaluation data. This article, the first in a dialogue exchange, examines how decisions about measurement are (and should be) made, especially in the context of small-scale local program…