Random samples of 4 items are selected from a manufacturing process at regular intervals and a certain quality characteristic is measured. After 25 samples, $\Sigma$ X = 15,350 and $\Sigma$ R = 411.4
To construct a mean chart, what is the upper control limit (UCL) for the mean?
A) 614.00
B) 411.4
C) 625.996
D) 3837.5

Question

Quizplus · Accepted Answer

To construct a mean chart, we need to find the control limits for the mean. 
UCL = X + A2*R/sqrt(n)
Here, n = 4 (since we are sampling 4 items at a time)
A2 = 0.729 (from the control chart constant table)
X = 15,350/25 = 614
R = 411.4
Plugging in the values, we get UCL = 614 + 0.729*(411.4/sqrt(4)) = 625.996. 
Therefore, the answer is option C.

Random Samples of 4 Items Are Selected from a Manufacturing Σ\SigmaΣ

Random Samples of 4 Items Are Selected from a Manufacturing $\Sigma$