Linear Regression in SAS

[Allegra]

For linear regression in SAS using proc reg, assuming I have a categorical independent variable coded "0" and "1", what level does sas automatically use as the reference?  and Is there a way to specify what level to be used as a reference?

Thank you

[PGStats · Accepted solution]

The reference level is the one coded number zero, by definition. To change the reference, exchange the codes.

For easier and more sophisticated handling of categorical effects, use a regression procedure that allows the CLASS statement, such as GLM, MIXED or GLIMMIX.

[Allegra]

Thank you so much for your response:)