Lagged Versus Difference Score Regression: An Example From a Community-Based Educational Seminar Evaluation:

Objectives. To demonstrate the use of evaluation data in determining the effectiveness of a series of community-based educational seminars designed to educate substance abuse treatment counselors on the latest science regarding the effects of alcohol abuse on diseases of the liver and pancreas; in the process, to highlight the use of difference scores versus lagged regression as alternative approaches to conducting such evaluations. Methods. Data were collected from 338 seminar participants during 4 half-day seminars in 2007, 2009, 2010, and 2014. Pre- and post-seminar data were collected immediately before and after the seminar, approximately 3 hours apart. Survey questions included demographics and a series of multiple-choice knowledge questions that were identical at pre- and posttest. Results. Analyses showed that, on average, participants improved their knowledge by 19.7 percentage points from 0.44 to 0.63, or 44.7%. Factors associated with learning using difference scores revealed that only survey w...