# Variance Components Model

**Specify Model.** A full factorial
model contains all factor main effects, all covariate main effects,
and all factor-by-factor interactions. It does not contain covariate
interactions. Select Custom to
specify only a subset of interactions or to specify factor-by-covariate
interactions. You must indicate all of the terms to be included in
the model.

**Factors & Covariates.** The factors and covariates are listed.

**Model.** The model depends on the nature of your data. After selecting Custom, you can select the main effects
and interactions that are of interest in your analysis. The model
must contain a random factor.

For the selected factors and covariates:

- Interaction
- Creates the highest-level interaction term of all selected variables. This is the default.
- 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.

**Include intercept
in model.** Usually the intercept is included in the model.
If you can assume that the data pass through the origin, you can exclude
the intercept.

Specifying Models for Variance Components

This feature requires Custom Tables and Advanced Statistics.

- From the menus choose:
- In the dialog box, click Model.
- In the Model dialog box, select Custom.
- Select one or more factors or covariates, or a combination of factors and covariates.
- Select a method for building the terms.
- Repeat these steps until you have all of the terms you want in the model. At least one random factor must be included in the model. Do not use the same term more than once in the model.

You can deselect the intercept.