To clarify my initial question regarding performing an interrupted time series analysis, I'm looking at time series data before during and after an intervention to see if the intervention resulted in a change to the data. Based on visual inspection of the time series plot there is a large change in the level and a trend change through out the time series. I'm attempting to do something like what is described in the following reference:Elligsen, M., Walker, S. A. N., Pinto, R. Infect Control Hospital Epidemiol 2012;33(4):354-361 Thank you for your assistance Michael Ott Sent from my iPhone