Hi, I am running a simple linear regression in proc glm: y = x + a + x*a, where y is days of sickness absence per year, x is calendar year (treated as a continuous variable) and a a cohort effect (two categories). I would like to know whether the change in y over the time is different for my two cohorts. I have the estimates for my two slopes and so far I am fine. However, I get stuck when I try to get the 95% confidence intervals to go with each of the estimates. Could someone help me out? Thanks in advance!
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