Is it meaningful to use 'dropterm' (MASS) on a fitted coxph (survival) model with a frailty term? Trying to do so gives results that do not look meaningful (to me), so my guess is that the answer to my question is 'No'. So, what is the recommended way of comparing nested mixed-effects models in general? -- G??ran Brostr??m tel: +46 90 786 5223 Department of Statistics fax: +46 90 786 6614 Ume?? University http://www.stat.umu.se/egna/gb/ SE-90187 Ume??, Sweden e-mail: gb at stat.umu.se