Participation in a Control Group

What happens to participants in the control condition? Can they receive other kinds of services?

Participants assigned to the control condition can have access to any services not provided by the program or intervention being studied. For instance, parents of a student assigned to a control condition in a study of an afterschool program could seek out some other type of afterschool care for their child. It is important for evaluators to collect data about the services that control group members receive so that they can better interpret the evaluation’s findings.

Will participants in the control group ever have an opportunity to receive the new services?

Assuming the new program proves effective, which we do not know prior to the evaluation, participants in the control condition can become eligible for the new program as soon as the study is complete. Having participants in the control condition be first on the list for enrollment in the new program once the study is complete can be an incentive for participation.

Are there situations in which random assignment is or isn’t appropriate?

If the consequences of random assignment create a situation that is potentially harmful to some students who might end up in the control condition, it would be appropriate to exempt those students from the research. For instance, in planning for an impact study of the effects of Head Start, the federal early childhood program for children in poverty, evaluators might decide to exempt children with the highest need from participation in random assignment. However, both the exemption procedures and the circumstances under which students are exempted should be firmly established before the study begins. In turn, study results are not applicable to students who are exempted.

What happens if a participant "drops out" of the program after being randomly assigned to the intervention group?

Participants who drop out of a program or intervention will be viewed as if they were still part of the study. That is, researchers will continue to collect followup data from all participants in the study regardless of whether they drop out. This allows researchers to assess the extent to which dropping out influences the effects of the program. It also prevents the problem of a new program appearing to be more effective than a control condition because participants making less progress drop out of the new program at higher rates than they drop out of the control condition.

What would you gain by participating in a program evaluation?

Participating in an education program evaluation has many advantages. First, it gives schools, teachers, and students an opportunity to help policymakers learn what education practices or interventions are particularly effective. Right now, we have very little information on what works and what doesn’t. Only with the assistance of schools, teachers, and students can those who design education programs really learn what will make education more equitable and efficient for all children. Second, study results can help school districts, for example, make better decisions about the education practices they regularly use and about new practices that they may use on a larger scale in the future. Third, participating in an evaluation may give school districts and schools access to resources that might not otherwise be available. Finally, participating school districts, schools, and students will also be the first to reap the benefits of new and possibly innovative programs if the findings indicate that the programs are effective. The 50 percent chance of experiencing a new, exciting, and potentially important educational innovation that comes though participating in a randomized study is often much better odds than are available for those students and schools that don’t participate at all and thus don’t have access to the innovation.

This project was supported under contract number ED-01-C0-0039 (0002), as administered by the Institute of Education Sciences, U.S. Department of Education. This publication is in the public domain. Authorization to reproduce it in whole or in part for educational purposes is granted.