The Weibull, lognormal and gamma distributions are popular models for lifetime data. but in applications such as strength of materials, the Weibull distribution generally provides t,he most plausible physical model for failure data. However, the conventional Weibull plot may display a curve at the lower end, and is often handled by fitting a third (threshold) parameter or by using another model such as the lognormal distribution. These approaches may yield significant variations when the models are used for prediction purposes. The data collected can lack a representative number of observations in the lower tail because experimental strength data may sometimes be incomplete due to some weak experimental units not surviving to be tested. In this paper a ‘selection probability function’ is proposed which represents the probability that a unit of given strength survives to be tested. Simulations show that this function when combined with an underlying Weibull strength distribution, yields a distribution simi...