Model (Complex Samples Cox Regression)

Specify Model Effects. By default, the procedure builds a main-effects model using the factors and covariates specified in the main dialog box. Alternatively, you can build a custom model that includes interaction effects and nested terms.

Non-Nested Terms

For the selected factors and covariates:

Interaction. Creates the highest-level interaction term for all selected variables.

Main effects. Creates a main-effects term for each variable selected.

All 2-way. Creates all possible two-way interactions of the selected variables.

All 3-way. Creates all possible three-way interactions of the selected variables.

All 4-way. Creates all possible four-way interactions of the selected variables.

All 5-way. Creates all possible five-way interactions of the selected variables.

Specifying Non-Nested Build Terms

This feature requires the Complex Samples option.

1. From the menus choose:

   Analyze > Complex Samples > Cox Regression...

2. Select a plan file. Optionally, select a custom joint probabilities file and then click Continue.
3. In the main dialog box, select factors and covariates and click Model.
4. Select Custom.
5. Select one or more factors or covariates or a combination of factors and covariates.
6. Select a method for building the terms from the Type drop-down list and add them to the model.
7. Repeat the process until you have all of the terms that you want in the model.

Nested Terms

You can build nested terms for your model in this procedure. Nested terms are useful for modeling the effect of a factor or covariate whose values do not interact with the levels of another factor. For example, a grocery store chain may follow the spending habits of its customers at several store locations. Since each customer frequents only one of these locations, the Customer effect can be said to be nested within the Store location effect.

Additionally, you can include interaction effects, such as polynomial terms involving the same covariate, or add multiple levels of nesting to the nested term.

Limitations. Nested terms have the following restrictions:

• All factors within an interaction must be unique. Thus, if A is a factor, then specifying A*A is invalid.
• All factors within a nested effect must be unique. Thus, if A is a factor, then specifying A(A) is invalid.
• No effect can be nested within a covariate. Thus, if A is a factor and X is a covariate, then specifying A(X) is invalid.

Specifying Nested Build Terms

1. From the menus choose:

   Analyze > Complex Samples > Cox Regression...

2. Select a plan file. Optionally, select a custom joint probabilities file and then click Continue.
3. In the main dialog box, select factors and covariates and click Model.
4. Select Custom.
5. Select a factor or covariate that is nested within another factor and then click the move button.
6. Click Nesting.
7. Select the factor within which the previous factor or covariate is nested and then click the move button.
8. Click Add to Model.
9. Optionally, you can include interaction effects or add multiple levels of nesting to the nested term.