Random samples of four items are selected from a manufacturing process at regular intervals and a certain quality characteristic is measured. After 25 samples,ΣX = 15,350 and ΣR = 411.4. To construct a mean chart,what is the upper control limit for the mean?
A)614.00
B)411.4
C)626.00
D)3837.5

Question

Quizplus · Accepted Answer

To construct the mean chart, we need to first calculate the values of X-bar and R-bar:
X-bar = ΣX/n = 15,350/100 = 613.5
R-bar = ΣR/n = 411.4/100 = 4.114

Next, we need to calculate the control limits for X-bar chart:
Upper control limit = X-bar + A2*R-bar
Lower control limit = X-bar - A2*R-bar

From the standard normal distribution table, the value of A2 for n=4 is 0.73.

Plugging in the values, we get:
Upper control limit = 613.5 + 0.73*4.114 = 626.00

Therefore, the correct answer is C.

Random Samples of Four Items Are Selected from a Manufacturing