Logistic Regression Type III analysis DF = 0 estimate missing

[laura72]

Hi, I ran a proc logistic on a binary response with a few covariates, some continuous and some categorical. When I checked the TYPE III analysis of effect, there is one line for a categorical covariate with DF = 0 and missing estimate. What is wrong here?

TYPE III Analysis of Effect

Effect   DF Chi-square     Pr>Chisqr

Age        1   58999.5037  <.0001

Indicator  0   .                   .

gender    1   3266.6988   <.0001

[Reeza]

What does proc freq on the variable (indicator) do, with similar modelling restrictions (ie any where clause you used)?

[Doc_Duke]

Logistic Regression has a linear model component.  If any variable can be expressed as a linear combination of others, then it will show up with 0 degress of freedom and no estimate.

For instance, if you had 0-1 binary variables called Female and Male, then <Female = 1 - Male> and one of them is redundant.  Usually, it is not as bovious as my example and you might need to do some two way frequencies or correlations to tease out the dependency.

Doc Muhlbaier

Duke