Question

Reliably establishing causality is a critical element in most empirical research. Regression discontinuity is another technique to establish causality. Describe the idea of regression discontinuity.

Answer 1

A regression discontinuity design (RDD) is a quasi-experimental pretest-posttest design that elicits the causal effects of interventions by assigning a cutoff or threshold above or below which an intervention is assigned. By comparing observations lying closely on either side of the threshold, it is possible to estimate the average treatment effect in environments in which randomization is unfeasible. First applied by Donald Thistlethwaite and Donald Campbell to the evaluation of scholarship programs, the RDD has become increasingly popular in recent years. Recent within-study comparisons of randomised controlled trials (RCTs) and RDDs have empirically demonstrated the internal validity of the design.

The ideas of RDD are as follow:

• When properly implemented and analyzed, the RDD yields an unbiased estimate of the local treatment effect. The RDD can be almost as good as a randomized experiment in measuring a treatment effect.
• RDD, as a quasi-experiment, does not require ex ante randomization and circumvents ethical issues of random assignment.
• Well-executed RDD studies can generate treatment effect estimates similar to estimates from randomized studies.

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