Cluster randomized trials, or trials in which clusters such as schools, communities, or organizations are randomly assigned to condition, are being used more frequently to evaluate the effectiveness of a program, policy, or practice. However, if a CRT is not designed with adequate statistical power to detect a meaningful effect, it will not yield rigorous evidence as to whether or not a program is effective. This presentation will introduce the Optimal Design Plus Software, a free and user-friendly program for conducting power analyses for CRT’s. A short demonstration of the software will be included. #WebinarSeries #QuantitativeMethods-TheoryandDesign