The Immortal Time Bias in Observation Analysis

There's a reason why there's a lot of studies that are bias ine literature. We cannot look into the future for time zero to decide who is in its group. Without looking into the future, some investigators are lost because they don't kno to classify people if they know what they are going to be doing. So once we have adjusted for ses a bioses yer between the two treatment groups, we can only adjust for the variable set we have observed,. not for those sat we haven't observed, or haven't observed correctly enough. That is e fundamental problem, of course, of opservational classes. How do you kind of communicate how much hol robustianals