Interrupted time series (ITS)

Method of causal inference that is often used when randomisation is not feasible. The method involves measuring some outcome multiple times both before and after the implementation of an intervention. This allows researchers to identify both the pre-intervention level and trends, which can then be compared to levels and/or trends post-intervention. In other words, the pre-intervention population serves as the counterfactual against which the post-intervention population is compared.