Methods for detecting influential observations for the Weibull model fit to censored data are discussed. These methods include: one-step deletion diagnostics, influence functions and curvature diagnostics. Results indicate that the curvature diagnostics may be helpful in detecting masking.

Consider testing for equality variances in a one-way analysis of variance. Levene's test is the usual F-test for equality of means computed on psuedo-observations, which one defines as the absolute deviations of the data points from an estimate of the group 'center'. We show that,...