Using large enough generated sample of Ii values, the overall probability density distribution of leakage current was produced and is shown in Fig. 6a. Search was made for the standard probability function that best fits that distribution and was found to be the Weibull distribution. The Weibull distribution has the ability to assume the characteristics of many different types of distributions. This has made it extremely popular among engineers and quality practitioners, who have made it the most commonly used distribution for modeling reliability data. It is flexible enough to model a variety of data sets, and having displayed the best fit to the present case study, it has been adopted. It is expressed by:
(7)
whose parameters are λ = 49.7 and k = 0 0.344; its mean is 67.5 mA, and the standard deviation is 21 mA with a square error = 0.018915.