Weibull probability paper used on highly stressed bimodal components

Under high stress conditions the ‘freak’ and ‘strong’ subpopulations lie very close to each other on the time scale. It is easy to ‘read’ such a time-to-failure distribution as unimodal, especially when probability paper is used. This paper puts forward Parzen'sestimator of the probability density function as a very useful method of indicating the ‘freak’ subpopulation.