“…An important characteristic of a Weibull distribution is that its failure rate is decreasing for < 1, constant for = 1, and increasing for > 1. Several characterizations of mixture of distributions (for example, exponential, hyperexponential, gompertz, Rayleigh, and generalized power function distributions) -based on conditional expectations of order statistics -have been extensively discussed by Nassar and Mahmoud (1985), Nassar (1988), El-Arishy and Ahmed (1996), Wu and Lee (1998a,b), , Navarro and Ruiz (2004), Nassar (2005Nassar ( , 2006, and Lee et al (2011). As for the characterizations of mixture of Weibull distributions, in this article we propose an extension of the results of Khan and Ali (1987).…”