Specifying the omitted category of a categorical explanatory variable

Models with categorical explanatory variables have a coefficient associated with every category except for one; this is called the omitted category. The other category coefficients are relative to the omitted category coefficient, which is zero by construction.

To specify the omitted category of an explanatory variable:

1. In the Model view, select the explanatory variable whose omitted category you wish to set
2. Choose Model > Explanatory Variable > Set Omitted Category, and select the desired category to omit

The default is to omit the first category from the model.

See also:

• Treating an explanatory variable as categorical data
• Setting the base outcome of a categorical outcome variable
• About models

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