What Does It Mean When a Study Finds No Effects?

Suppose you work for a school or district and need to make a decision about a program. For instance, maybe you are thinking about switching curricula or implementing a new schoolwide intervention aimed at behavior. You pick up a study of the program and read that there is no effect. What could have caused that result, and what does it mean? This brief explains what to look for in a study that finds no effect and how you can think about what to do next.

To measure program effectiveness, research studies compare outcomes for a group that received a program to outcomes of a group that did not. When a difference is not likely due to chance alone (that is, it is statistically significant), we say that the program had an effect.