You can use the Variables tab to specify the variables for the Logistic Regression analysis. The Variables tab is shown in Figure 23.2.

The analysis handles two types of models. For single-trial syntax, you specify a single binary variable as the response variable. This variable can be character or numeric. For events/trials syntax, you specify two numeric variables that contain count data for a binomial experiment. The value of the first variable is the number of positive responses (or events). The value of the second variable is the number of trials.

The dialog box supports multiple explanatory variables. You can include nominal variables in the model by adding them to the Classification variables list. You can include interval variables in the model by adding them to the Quantitative variables list.

When you add an explanatory variable, that main effect is added to the Effects tab. You can add interaction effects and nested effects by using the Effects tab.