Mathematical Model for Suppression of Glucocorticoid Secretion by Using a Log-logistic Step-stress Model

This paper presents an optimum plan for simple (two stresses) time-step-stress accelerated life tests under the log-logistic model considered appropriate for insulating materials. A log-logistic life distribution with a median that is a log-linear function of stress, and a cumulative exposure model are assumed. The optimum test plan is obtained by minimizing the asymptotic variance of the maximum likelihood estimator (MLE) of the median life at a design stress. A cumulative exposure model holds, that is the remaining life of any test unit depends only on the cumulative exposure it has seen. Application part given in this paper is tested for glucocorticoid hormones of humans and animals. Mathematical Classification: 60 Exx, 62 Exx, 62 Hxx.