The Random Fatigue Life Model as a special case of the RMM model- A comment on ‎Pascual (2004)‎

In a recent paper, Pascual (2003a) introduced a standardized form of the Random Fatigue-Limit (RFL) Model. This is the most recent in a series of papers in which Pascual and Meeker and Pascual have introduced and elaborated on this model (Pacsual and Meeker, 1997, 1999; Pascual, 2003a,b, and references therein). Unfortunately, Pascual (2003a) failed to realize that the RFL model is in fact a special case of the RMM model (where RMM stands for Response Modeling
Methodology), introduced recently (Shore, 2002a,b, 2003, 2004a). That this is the case may first be realized by comparing the form of the density function and the cumulative distribution function of the log life, Z, in Pascual (2003a) to the corresponding expressions for the error distribution of the RMM model derived in Shore (2002b). However, the fact that the RFL model is a special case of the RMM model was already indicated and discussed at some length in Shore (2002a), where a numerical example comparing the results obtained from applying the two models to the same data set was worked out (the approximate ML estimation procedure for the RMM model introduced therein has meanwhile being appreciably improved; Refer to Shore, 2004b).