Using both natural experiments and randomized controlled trials, we examine the impact of interventions. In natural experiments, we take advantage of the fact that lotteries or waitlists create naturally occurring control groups. We use these to examine the impact of an intervention, comparing those who received it to those who, due to resource limitations, didn’t.
Randomized controlled trials (RCTs) compare the impact of an intervention for people randomly selected to receive different interventions. We employ randomized controlled trials when, due to resource limitation, the intervention will be offered to a subset of the population under ordinary conditions. RCTs are considered the gold standard of research for many questions.