Question:-
A control chart is established with limits of ± 2 standard errors for use in monitoring samples of size n = 20. Assume the process to be in control. What is the likelihood of a sample mean falling outside the control limits?
Option (A)
97.7%
Option (B)
95.5%
Option(C)
4.5%
Option(D)
2.3%
Correct Option:
(C)
Question Solution:
P(2) – P(2) = 0.9545
Sample falling outside control limit = 1 – 0.9545 = 0.0455 = 4.55%

question-answer-faq-8851