DISCRETE SCALE MODELS FOR SURVIVAL-SACRIFICE EXPERIMENTS

Analyses of carcinogenicity experiments involving occult (hidden) tumo urs are usually based on cause-of-death information or the results of many interim sacrifices. A simple compartmental model is described tha t does not involve the cause of death. The method of analysis requires only one interim sacrifice, in addition to the usual terminal kill, t o ensure that the tumour incidence rates can be estimated. One advanta ge of the approach is demonstrated in the analysis of glomeruloscleros is following exposure to ionizing radiation. Although the semiparametr ic model involves fewer parameters, estimates of key functions derived in this analysis are similar to those obtained previously by using a nonparametric method that involves many more parameters.