In an (appropriately) private reply, Noah SIlverman told me that "cost effectiveness study" is a well-defined term in epidemiology and that my frustration at his vague description was therefore just a reflection of my ignorance. I accept that and wish to publicly acknowledge my error. My apologies to Noah and the list. -- Bert -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm