Regression is a statistical method for estimating the relationship between one or more predictor (independent) variables and a criterion (dependent) variable. Conventionally, regression studies have focused on the correlation between the predictors and the criterion variable. However, regression is a highly flexible approach to data analysis that can be used to compare differences on mean scores of the dependent variable from different categories of one or more independent variables. This application is equivalent to the statistical methods analysis of variance and analysis of covariance. An evaluator could use regression to estimate the effects of an intervention on an outcome variable, controlling for demographic variables of the program participants and control subjects.