The average defect rate for our product is 0.18. Our sample size is 100.
Calculate the upper limit for a p-chart (using z=3, as we always do for these).
Expert Answer
p_bar = 0.18
n = 100
The standard error can be written as –
S_p=sqrt{frac{bar{p}(1-bar{p})}{n}}
or, Sp = sqrt(0.18*(1-0.18)/100) = 0.0384
UCL = p_bar + 3.Sp = 0.18 + 3*0.0384 = 0.2953