Linear regression analysis allows researchers to predict scores on a dependent or criterion variable (Y) based on knowledge of an independent or predictor variable (X). Simple linear regression involves using one predictor variable to predict scores on the dependent variable. Multiple regression expands this to use multiple predictor variables. Key aspects of regression analysis covered in the document include the correlation between variables, using the least squares method to determine the best fitting regression line, computing predicted Y scores, explaining and unexplained variance, and the importance of multiple regression in understanding how well predictor variables predict the criterion variable.