Winterbottom stated that if X is a binomial random variable with sample size n and parameter p, then Y = X/n is a binomial proportion with μ = E (Y) = p, and central moments of Y,μ2 = V(Y)=p(1−p)/nandμ3 =p(1−p)(1−2p)/n2.Then,Yα (namedhereYα(1)),isobtainedfrom the Cornish–Fisher expansion with only one correction term as: