David E. Matthews

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A frequently recurring question posed by leukemia researchers concerns a test of a constant failure rate against the alternative of a failure rate involving a single change-point. In answer to this question, a likelihood ratio test appropriate for the stated alternative is derived and simulated. Consideration is given also to tests based on alternatives in(More)
This paper considers estimation of a survival function when there exists a change point and the survival time of interest is defined as elapsed time between two related events. Furthermore, there exists censoring on observations on the occurrences of both events and truncation on observations on the occurrence of the second event and thus the survival time(More)
In medical studies, it is often of scientific interest to evaluate the treatment effect via the ratio of cumulative hazards, especially when those hazards may be nonproportional. To deal with nonproportionality in the Cox regression model, investigators usually assume that the treatment effect has some functional form. However, to do so may create a model(More)
We propose graphical diagnostic tools to assess the fit of a bivariate accelerated lifetime regression model. Using univariate residuals for each response measurement in a pair, we assess their dependence structure via the bivariate probability integral transformation of univariate residuals, which we call V-residuals. To reduce the computational burden(More)
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