Multiple Regression Analysis, Multi-collinearity Model Testing, When Two or More Independent Variables Measure Same Thing, (Standard Errors are Large), Is Linear Regression Model Better When X's (Independent Variables) Are Combined Versus Used Separately ??, (1) Calculate Correlation Matrix (Multicollinearity), Need High Degree Correlation Between Y-Dependent & X's Independent Variables & (2) Need Low Degree Correlation Between X's Independent Variables, then Each X's Contribute To Regression Model, 𝐑^𝟐 always increases when Variables are added, but How does it affect 𝐑_𝐀𝐃𝐉 ??, Check If R Increases Or Decreases Upon Adding a Variable, detailed example by Allen Mursau