Glossary
Process evaluation
What is process evaluation?
Process evaluation examines how an intervention was delivered, how participants responded, and how context influenced its operation. It complements outcome evaluation, which asks what changed.
What it can show
Relevant questions include whether the planned content reached participants, how delivery changed, and whether the proposed mechanisms appear plausible. The findings can help explain results, but do not automatically distinguish an ineffective theory from poor delivery. Those explanations require evidence.
Process evaluation example
Imagine a workplace stress program that produces little measurable change. In this hypothetical case, attendance records show that only 30 percent of eligible employees attended: limited reach. Delivery logs show that sessions planned for 60 minutes lasted 30 minutes: reduced fidelity to the planned delivery and a lower delivered dose. Interviews indicate that managers discouraged attendance during busy periods: a contextual barrier. Together, these observations suggest that employees received less of the planned program and help explain why. They do not prove that the program’s theory was sound or that ideal delivery would have produced a benefit.
Why process evaluation matters
The Medical Research Council guidance by Moore and colleagues organizes process evaluation around implementation, mechanisms, and context. It recommends making causal assumptions explicit so they can be examined alongside outcome evidence.