In PROC LOGISTIC with CLASS variables, which parameterization uses the last alphabetically sorted category as the reference by default?
Select an answer to reveal the explanation.
Short Explanation
Here's the deal — you want reference coding, because PROC LOGISTIC's default CLASS parameterization uses the last alphabetically sorted category as the reference. The other choices are effect coding, deviation coding, or polynomial contrasts, not the default reference setup.
Full Explanation
The default PROC LOGISTIC CLASS parameterization is PARAM=REF, using the last alphabetically sorted category as the reference, so dummy variables compare other levels to it. PARAM=GLM is effect coding used in PROC GLM. PARAM=DEVIATION compares each level to the grand mean. PARAM=ORTHPOLY uses polynomial contrasts for ordered variables.