I don't know how to change my continous (yob) variable to discrete. I wanted the categories to look like this  2001-1984 (21-32) 1983-1973 (33-43) 1972-1962 (50-60) 1961-1951 (61-71) ... View more

I'm not sure if this is how you analyze confounding with possible interaction (effect modification). The predictor is opioid usage while the outcome variable is prevalence of prior injection drug usage. I am creating my models through logistic regression  Only confounder in model was SES in model, possible effect modifier was ethnicity. This was the SAS code I used looking at confounding and possible effect modification.  proc logistic data=work.ex4; class opioid_use SES eth_2 (ref= '3. Caucasian')/ param=ref; model ever_inject = opioid_use SES eth_2; run;  Based on multivariate logistic model, I don't have effect modification only confounding      ... View more