1 binary response/person

From: LSheiner <lewis@c255.ucsf.edu> Subject: 1 binary response/person Date: Mon, 17 Sep 2001 11:29:23 -0700 All - There's been an exchange recently about whether one can estimate a hierarchical model given only a single binary response from each individual. I claimed it couldn't be done, by which I meant that OMEGA would be meaningless. Stu Beal, in a personal reply to me (which I shared with nmusers) pointed out that my claim that it couldn't be done was not strictly true, in the sense that NONMEM will not necessarily terminate in rounding errors. But he did not claim that the estimate of the structural parameters (theta's) would be good, and he made no claim whatever about OMEGA. Perhaps there are circumstances in which taking a MEM view of single binary response per person data is helpful, but experience to date indicates that if such circumstances exist, they are hard to find. All my experience to date suggests that estimates of those parameters that are common to both the hierarchical and non-hierarchical formulations are actually more precisely estimated under the latter, and estimates of the parameters unique to the hierarchical formulation, namely OMEGA, are meaningless. LBS. -- _/ _/ _/_/ _/_/_/ _/_/_/ Lewis B Sheiner, MD (lewis@c255.ucsf.edu) _/ _/ _/ _/_ _/_/ Professor: Lab. Med., Bioph. Sci., Med. _/ _/ _/ _/ _/ Box 0626, UCSF, SF, CA, 94143-0626 _/_/ _/_/ _/_/_/ _/ 415-476-1965 (v), 415-476-2796 (fax)