Most education research studies concern a particular education treatment or intervention, for example, a reading program, a type of teacher preparation or a mathematics curriculum designed to improve practices or conditions. (In experimental research, the treatment is called the independent variable.) Researchers should provide the operational definition of the treatment being studied. In addition, the definition should have construct validity.

Caution:
Always determine the operational definition of the treatment in a study. Many research claims are invalid because the actual treatment in the study has been mislabeled.

As an example of an operational definition, consider a study of the effects of teacher professional development on student achievement. The treatment in this study is professional development. An operational definition of professional development could be a class in literacy instruction that teachers attend after school two times each week. Most educators would probably agree that this treatment is a valid example of professional development. If the operational definition were that teachers go out to lunch twice a week, most educators would object to calling this professional development. The treatment should be defined in a way that is a valid example or representation of the treatment being studied, in this case, professional development.

Some treatments in education are particularly difficult to define. For example, researchers define teacher content knowledge (e.g., knowledge of mathematics) in various ways, such as the number of college courses the teacher completed in a subject area, whether the teacher earned a college major or minor in a subject and the teacher’s scores on teacher licensing tests. All these measures are proxy measures for the actual knowledge teachers have about a particular content area. When a proxy measure is used, valid conclusions can be made only about the measure and not about the construct the measure represents (in this case, actual knowledge).

In addition to a valid definition, the treatment must be implemented consistently. Researchers should report measures that demonstrate treatment fidelity. Did the treatment occur as planned?

If the treatment, for example, is a professional development class in literacy instruction, the researcher should report information and measures that demonstrate the class occurred as planned. This information might include participant attendance, content of the instruction, class schedule and class activities. In addition, if any event occurred during the treatment that might influence the results, for example, a literacy conference that some of the teachers attended during the study, it should be reported. The literacy conference might interact with the professional development, making the treatment appear to be more effective than it was.