Building a Model

Requirements for Building a Model

Create a Main Effect

Create Crossed Effects (Interactions)

Create a Nested Effect

Create a Full Factorial Model

Create an N-Way Factorial

Requirements for Building a Model

By default, no effects are specified, which results in the task fitting an intercept-only model, so here is what you see on the Models tab.

Models Tab with Only the Intercept as an Effect

To specify a model effect, you must assign at least one variable to the Factors role. On the Models tab, click Edit to open the model builder.

When you close the model builder any effects that you created appear on the Models tab.

Models Tab with Intercept and Team as an Effect

Create a Main Effect

Select the variable name in the Variables box.
Click Add to add the variable to the list of model effects.

Create Crossed Effects (Interactions)

Select two or more variables in the Variables box. To select more than one variable, press Ctrl.
Click Cross.

Create a Nested Effect

Nested effects are specified by following a main effect or crossed effect with a classification variable or list of classification variables enclosed in parentheses. Here are examples of nested effects: B(A), C(B*A), D*E(C*B*A). In this example, B(A) is read "B within A."

Select the classification variable in the Model Effects Builder.
Click Nest. The Nested window appears.
Select the variable to use in the nested effect. Click Outer or Nested within Outer to specify how to create the nested effect.

Note: The Nested within Outer button is available only when a classification variable is selected.
Select the effect that you want to nest.
Click Add.

Create a Full Factorial Model

Select two or more variables in the Variables box.
Click Full Factorial.

For example, if you select the Height, Weight, and Age variables and then click Full Factorial, these model effects are created: Age, Height, Weight, Age*Height, Age*Weight, Height*Weight, and Age*Height*Weight.

Create an N-Way Factorial

Select two or more variables in the Variables box.
Click N-way Factorial and specify the value of N.

For example, if you select the Height, Weight, and Age variables, click N-way Factorial, and then specify the value of N as 2, these model effects are created: Age, Height, Weight, Age*Height, Age*Weight, and Height*Weight. If N is set to a value greater than the number of variables in the model, N is effectively set to the number of variables.