“…However, as Siddall (1983) pointed out, if there is uncertainty about a random variable except for its bounds, then uniform distribution might be an excellent option to represent that variable. Many researchers designed control charts assuming that the process shift follows uniform distribution ( Castagliola, Celano, & Psarakis, 2011 ; Domangue and Patch, 1991 , Sparks, 2000 ), while others used beta distribution ( Ou, Wu, & Goh, 2011 ) and Rayleigh distribution (Wu, Shamsuzzaman& Pan, 2004; Haridy, Maged, Kaytbay, & Araby, 2017 ) to describe the process shift.…”