You can use the **Roles** tab to specify a frequency variable or weight variable for the analysis. (See Figure 23.14.) You can also specify an *offset variable*.

A frequency variable is a numeric variable whose value represents the frequency of the observation. If you use a frequency variable, the underlying procedure assumes that each observation represents observations, where is the value of the frequency variable.

A weight variable is a numeric variable with values that weigh each observation in the regression.

An offset variable is a special explanatory variable. The regression coefficient for this variable is fixed at 1. This corresponds to the OFFSET= option in the MODEL statement.