Hi, Reeza Sorry for the delay. My intention is to get the 95% CI and PI for pre-defined groups. For short, the y response variable is average daily dose (mg), for example, and the predictor variables including continuous quantitative variables such as age, body surface area, serum concentration of albumin, and other dummy (qualitative) variables such as whether the congestive heart failure present, whether specific genotype present, whether hospitalization for longer than 14 days, etc. Obviously, the each qualitative variables divided these patients into two subgroups (the condition present or not). I want to know the 95% CI and PI for both subgroups. It's that when I am investigating the 95% CI and PI for both groups divided by a specific dummy variable, other predictor variables are adjusted (by the inherent nature of linear regression). I want to get the 95% CI and PI for the both subgroups. Tom
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