Each item sampled, X, is a discrete random variable denoting the number of trials that result in an outcome of interest, with a binomial distribution of parameters n and p, where n is the number of trials, p is the probability of finding a nonconforming item and (1 − p) is the probability of finding an item without defect. It is further assumed that the n observations of X are independent, that is, the probability of finding a nonconforming item in a sample is independent of the previous sample nonconforming items. The sample proportion P , is defined as P = X /n (relative binomial) with mean, variance and standard deviation as given in Section 2.1.