Thirty samples of size 1200 were drawn from a manufacturing process and the number of defectives in each sample was counted.The mean sample proportion was 0.04.The upper control limit for the 3-sigma p chart is:
A) 0.0170.
B) 0.0570.
C) 0.1518.
D) 0.0230.

Question

Quizplus · Accepted Answer

The upper control limit for the 3-sigma p chart can be calculated as:
UCL = p̂ + 3√((p̂(1-p̂))/n)
where, p̂ = 0.04 (mean sample proportion), n = 1200 (sample size)

Substituting the values, we get:
UCL = 0.04 + 3√((0.04(1-0.04))/1200)
UCL = 0.0570

Therefore, the best choice is B, with the calculated upper control limit of 0.0570.

Thirty Samples of Size 1200 Were Drawn from a Manufacturing