Introduction to quasi-experimental designs

What is a quasi-experimental design (QED)?

A QED is a type of evaluation design that estimates the causal impact of an intervention on a sample without random assignment.

There are many types of QEDs, but they all involve statistically generating a counterfactual (a way of simulating what would have happened if the intervention/programme had not taken place) without random assignment. The impact of the intervention can be measured by comparing the outcomes of the counterfactual and the intervention participants.

QEDs are commonly used in research and evaluation but knowing how to use them can be a challenge.

Planning a QED

Read this step-by-step guidance to learn about the key stages of running a QED: Diagnose, Plan, Measure, Reflect.

Videos

Introduction to QEDs

Find out more about QEDs in our video explainer.

Planning a QED (webinar and guide)

Watch our webinar on planning a QED, part of the ‘Evaluating causal impact’ series.

An introduction to QEDs: causal evaluation methodologies without randomisation

View our webinar session, ‘An introduction to QEDs: causal evaluation methodologies without randomisation’, part of our ‘Unlocking effective evaluation’ series in 2022. It includes:

• An introduction to quasi-experimental designs
• Difference-in-difference method
• Regression discontinuity design
• Q&A with the audience

QEDs: external resources

Find out more about QEDs. This list includes a range of books, articles and videos explaining the background, methodology and practice of QEDs.