Model Fitting: Logistic Regression |
You can use the Roles tab (Figure 23.14) to specify a frequency variable or weight variable for the analysis. 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 will be fixed at 1. This corresponds to the OFFSET= option in the MODEL statement.
Figure 23.14: The Roles Tab
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