Missing covariates

From: bvatul <bvatul@ufl.edu> Subject: Missing covariates Date: Mon, 02 Jul 2001 10:22:08 -0400 Hello All Could somebody please clarify this: I am analysing a data set in which I have covariates (wge, ht, wt, crcl) for 70% of the patients. Is it a good idea to substitute the median values of these covariates for the missing covariates ie., in patients in whom I dont have the covariates?In case we are substituting the median values and analysing the covariates is it still necessary to center the covariates? Are there any reported papers where the addition of missing covariates has led to misinterpretation of data? When should we substitute the missing covariates with the median values and when should we not? Thanks Atul