An educational intervention's effectiveness is judged by whether it produces positive outcomes for students, with the randomized controlled trial (CRT) as a valuable tool for determining intervention effects. However, the intervention-as-implemented in an experiment frequently differs from the intervention-as-designed, making it unclear whether unfavorable results are due to an ineffective intervention model or the failure to implement the model fully. It is therefore vital to assess fidelity of implementation and, where possible, to incorporate fidelity data in the analysis of outcomes. The objectives of this study are to: (1) elaborate a five-step procedure for fidelity assessment; (2) describe the advantages of assessing fidelity with this approach when conducting experiments testing educational interventions; and (3) use examples based on published studies to illustrate how this procedure can be applied. The authors find that, while most analyses of fidelity in educational studies include one or more steps in the five-step fidelity assessment process, the typical study does not include all steps and/or executes steps incompletely. As a result, the usefulness of fidelity data for interpreting experimental results is diminished. The authors demonstrate that a more complete assessment of fidelity in such cases would lead to a more meaningful analysis that interprets experimental results in light of actual implementation.