I'd like to propose a necessary improvement to the user experience when fitting Generalized Estimating Equations (GEE) models in SAS procedures like PROC GENMOD or PROC GEE .
The Current Problem
When fitting a GEE model, Likelihood Ratio Confidence Intervals (LRCI) are fundamentally unavailable because the GEE approach only specifies a mean-variance relationship and not a full likelihood function.
Currently, if a user specifies the LRCI option in the MODEL statement for a GEE, SAS simply ignores the option without any notification.
No warning or note is printed to the SAS log.
No message is added to the results output.
This silent behavior can mislead users into assuming the intervals were calculated or even that their model setup might be wrong, wasting time and potentially leading to misinterpretation.
The Proposed Improvement
SAS should implement explicit and multiple notifications when the LRCI option is requested for a GEE model:
1. Immediate Log Warning (Highest Priority)
A clear WARNING should be issued to the SAS log explaining the technical reason the option is ignored.
Suggested Log Message: WARNING: The LRCI (Likelihood Ratio Confidence Interval) option has been requested but is not supported for models fit using Generalized Estimating Equations (GEE). This is because GEE does not specify a full likelihood function. The option will be ignored, and default Wald confidence intervals will be reported.
2. Note in the Results Output
A brief note should be added to the output table (e.g., near the Parameter Estimates table) to confirm what was actually calculated.
Suggested Note in Results: Note: Likelihood Ratio Confidence Intervals (LRCI) were requested but could not be computed for this GEE model. Default Wald confidence intervals are reported.
Why This Matters
This is a critical usability improvement. GEE is a common and powerful method, and providing clear, instantaneous feedback prevents confusion, saves user time, and ensures that new or experienced users fully understand the inferential methods being used in their analysis.
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