Rigor in Quality Improvement Studies and the Role of Time-Series Methodologies—Reply

In Reply We thank Wong and Shojania and Kamal and Agrawal for their interest and commentary on our recent Editorial.¹ Wong and Shojania appropriately discuss the value of interrupted time series as a method to study quality improvement. A time series is a sequence of repeated measurements of an outcome over time. An interrupted time series is a sequence of repeated measurements taken both before and after the time series is “interrupted” by an intervention at a specific point in time. In theory, if the intervention is effective, the expected slope of the outcome measure based on measurements before the intervention should change significantly at the time of the intervention.