Interrupted Times Series Design
Interrupted time-series is an evaluation design that involves repeated measurement of an indicator over time, encompassing periods both prior to and after implementation of a program. The goal of such an analysis is to assess whether the treatment (or program) has "interrupted" or changed a pattern established prior to the program's implementation. However, the impact of alternate historical events may threaten the interpretation of the findings.
US Environmental Protection Agency. (2007). Program Evaluation Glossary. Office of the Administrator/Office of Policy/Office of Strategic Environmental Management/Evaluation Support Division.