# Linear Mixed Models Fixed Effects

This feature requires Custom Tables and Advanced Statistics.

**Fixed Effects.** There is
no default model, so you must explicitly specify the fixed effects.
Alternatively, you can build nested or non-nested terms.

**Include Intercept.** The intercept is usually included in the model. If you can assume
the data pass through the origin, you can exclude the intercept.

**Sum of Squares.** The method of calculating the sums of squares. For models with no
missing cells, the Type III method is most commonly used.

Specifying Non-Nested Build Terms for Linear Mixed Models

- From
the menus choose:
- Optionally, select subjects and repeated variables, and then click Continue.
- In the Linear Mixed Models dialog box, click Fixed or Random.
- Select Build terms.
- Select one or more factors or covariates or a combination of factors and covariates.
- Select a method for building the terms and click Add.
- Repeat the process until you have all of the terms that you want in the model.
- Select a type of sum of squares and whether or not you want the intercept.

Specifying Nested Build Terms for Linear Mixed Models

- From the menus choose:
- Optionally, select subjects and repeated variables, and then click Continue.
- In the Linear Mixed Models dialog box, click Fixed or Random.
- Select Build nested terms.
- Select a factor or covariate that is nested within another factor and click the move button.
- Click Within.
- Select the factor within which the previous factor or covariate is nested and click the move button.
- Click Add.
- Optionally, you can include interaction effects or add multiple levels of nesting to the nested term.