The CONTRAST statement enables you to conduct a statistical test that several expressions simultaneously equal zero. The expressions are typically contrastsâ€”that is, differences whose expected values equal zero under the hypothesis of interest.
In the CONTRAST statement you must provide a quoted string to identify the contrast and then a list of valid SAS expressions separated by commas. Multiple CONTRAST statements are permitted, and results from all statements are listed in a common table. PROC NLMIXED constructs approximate F tests for each statement using the delta method (Cox, 1998) to approximate the variance-covariance matrix of the constituent expressions.
The following option is available in the CONTRAST statement: