Model evaluation -- the process of making inferences about the performance of predictive models -- is a critical component of predictive modeling research in learning analytics. We survey the state of the practice with respect to model evaluation in learning analytics, which overwhelmingly uses only naive methods for model evaluation or statistical tests which are not appropriate for predictive model evaluation. We conduct a critical comparison of both null hypothesis significance testing (NHST) and a preferred Bayesian method for model evaluation. Finally, we apply three methods -- the na{\"i}ve average commonly used in learning analytics, NHST, and Bayesian -- to a predictive modeling experiment on a large set of MOOC data. We compare 96 different predictive models, including different feature sets, statistical modeling algorithms, and tuning hyperparameters for each, using this case study to demonstrate the different experimental conclusions these evaluation techniques provide.