What does an interrupted time series design analyze?

An interrupted time series design is specifically tailored to analyze data collected over multiple time points before and after a particular intervention or event is implemented. This design allows researchers to observe and measure the effects of the intervention on the subjects or phenomena being studied, providing a clear comparison of trends, levels, and changes attributable to the intervention over time. This method is particularly useful in determining the causal impact of an event or policy change, as it does not just capture the immediate effects but also any ongoing changes that occur afterward.

This design contrasts with methods that focus on data from a single observation point or participant responses in a single period, as it incorporates a broader temporal perspective. It also differs from simply analyzing demographic data, which does not involve the assessment of interventions or their outcomes. Thus, option B aptly captures the essence of what an interrupted time series design seeks to achieve by emphasizing the effects of an intervention over time.