You haven't shown the results of the test for the proportional odds assumption, which indicates whether you have a valid model. You might like to study the annotated output given here:   https://stats.idre.ucla.edu/sas/output/ordered-logistic-regression/ ... View more

@microdire27  - This appears to be a duplication of your question here (https://communities.sas.com/t5/Statistical-Procedures/Stratification-Using-SAS/m-p/670750#M32042 ).  See my response at that link.   SteveDenham ... View more

There have been a couple of threads about testing if a variable is a moderating variable in here lately, and it is something I am learning about as I go.  Given that, I don't think you can use a categorical variable in a regression without specifying a reference level (at least for non-full rank parameterization).  But with only two levels, it should not make a difference.  You could even treat the variable as continuous.   Yet another way to look at this as stratification would be to include the interaction between severity and time spent in the model.  Then using the SLICE statement, you could calculate the ORs for the simple effect of time spent at each level of severity. This would "stratify" the analysis in the sense that the ORs would be calculated within the "strata" of severity.  If that is acceptable, then good on you, and this all boils down to the definition of strata that SAS uses in its logistic regression procedures being different to what you are looking for.   SteveDenham ... View more

  Is it possible to stratify when you only have two levels? For instance, my outcome is sleep duration, while my exposure is read to. I am trying to determine if the third variable ADHD severity would modify the relationship between sleep duration and read to. All three are categorical variables. See below   Sleep Duration(1= Meet requirement, 2= do not meet) Read to (1= 0-3 days, 2= 4-6 days, and 3= Every day) ADHD Severity(  1= Mild and 2= Moderate/Severe)  My question is, is it possible to stratify based on ADHD severity. I think it is not possible since one of the levels of ADHD severity has to be a reference group. My current analysis did not stratify based on the level of ADHD severity (See attached  SAS output). I need clarification and if possible what is the appropriate SAS code. Thanks.  ... View more

  Is it possible to stratify when you only have two levels? For instance, my outcome is sleep duration, while my exposure is read to. I am trying to determine if the third variable ADHD severity would modify the relationship between sleep duration and read to. All three are categorical variables. See below   Sleep Duration(1= Meet requirement, 2= do not meet) Read to (1= 0-3 days, 2= 4-6 days, and 3= Every day) ADHD Severity(  1= Mild and 2= Moderate/Severe)  My question is, is it possible to stratify based on ADHD severity. I think it is not possible since one of the levels of ADHD severity has to be a reference group. My current analysis did not stratify based on the level of ADHD severity (See attached  SAS output). I need clarification and if possible what is the appropriate SAS code. Thanks.  ... View more