Hello all,

This is my first post on StataList (so you know I must really be stuck!) and it is regarding whether a certain type of analysis is possible.

I am looking to examine if the (binary logistic) regression output obtained from using a continuous operationalization of a predictor differs from the regression output using a categorical operationalization of that same predictor. I have regressed each operationalization independently on the same (binary) outcome using logistic regression; I have also saved the estimates for both, and compared/combined them using the -suest- command. However, when I run -test- following the -suest- command (i.e., test [continuous_iv = categorical_iv]), I receive this notice from Stata: "variables differ between equations. r(111)". Even though the continuous and categorical measures are derived from the exact same data (i.e., from the exact same responses from the same respondents), Stata does not recognize them as being equivalent and is unable to compare them.

The continuous measure is an 11-point scale from 0 to 10, and the categorical measure is simply a categorization based on that same scale that produces 3 possible levels (a score of 0-1 is coded as 2; 2-5 is coded as 2; and 6-10 is coded as 3). The continuous measure only produces one OR when regressed onto the outcome, while the categorical measure produces two ORs (because 1 of the 3 level is excluded from the regression model), and I assume this is why Stata is unable to compare the two model outputs..

Does anyone know of any workarounds to this using the -test- command, or of any similar commands that may allow for me to examine my research questions?


Also, if sample data would help to understand my analyses/problem, I can certainly create some!

Thank you for your time!