Introduction

When authors communicate the findings of their studies, there is often a focus on whether or not some intervention had the intended effect, and less attention to how much of an effect the intervention had. That is, it may be possible to state that some reading intervention increased reading scores more than the usual reading instructional techniques, but it is often more difficult for readers to determine how much of a difference the intervention made. Readers need to know if the intervention’s effects are large or small, meaningful or trivial. These guidelines describe the strengths and limitations of several approaches to the assessing the magnitude of an intervention’s effect. While there are few clearly right and wrong approaches, we do believe that some methods are better than others.