Regarding regression curves

[deleted_user]

Fellow SAS users,

This is more a statistics-related question and I request you kindly respond. I am trying to develop a regression model with time as one of the factors for a continuous dependent variable. There are three other independent variables in addition to time. After I run a linear regression using PROC REG with four independent variables and get the parameter estimates, can I use the predicted values for the dependent variable to draw curves in a plot of dependent variable versus time? Is it appropriate to just plot dependent var against time, when the equation was developed using other variables as well? Thank you.

[Paige]

You can do this, but you will have to fix the other independent variables to a certain value. When you plot dependent variable against time, you are plotting the main effect only. If there are interactions, this plot will not indicate interactions.

[deleted_user]

Thanks Paige.