You can use the Variables tab to specify the variables for the Polynomial Regression analysis.
The Variables tab is shown in Figure 20.3. The Y variable is the response variable. The dialog box supports a single X (explanatory) variable. To analyze a response that depends on multiple explanatory variables, you can use the Linear Regression (see Chapter 21: Model Fitting: Linear Regression) or the Generalized Linear Models (see Chapter 24: Model Fitting: Generalized Linear Models) analysis.