A Log-Linear Model for the Birnbaum-Saunders Distribution

The Birnbaum–Saunders distribution was derived to model times to failure for metals subject to fatigue. In this article, we formulate and develop a log-linear model for the Birnbaum–Saunders distribution. The model may be used for accelerated life testing or to compare the median lives of several populations. Methods of analyzing data for this log-linear model are discussed, with maximum likelihood and least squares methods being compared. It is found that, for commonly occurring conditions, the notorious intractability of the Birnbaum–Saunders distribution is not a serious problem because least squares and normal-theory procedures provide a reasonable alternative.