The mean of the sample means and the pooled standard deviation of 40 samples of size 5 taken from a production process under control are found to be 400 and 15,respectively.The lower control limit for the $\bar { x }$ chart is:
A) 460.37
B) 392.88
C) 379.88
D) None of these choices.

Question

Quizplus · Accepted Answer

The lower control limit for the $\bar { x }$ chart is:$ LCL = \bar { x } - 3 \frac { s } { \sqrt { n } } $$ LCL = 400 - 3 \frac { 15 } { \sqrt { 5 } } $$ LCL = 400 - 3 \frac { 15 } { 2.236 } $$ LCL = 400 - 3 \times 6.71 $$ LCL = 400 - 20.13 $$ LCL = 379.88 $

The Mean of the Sample Means and the Pooled Standard xˉ\bar { x }xˉ

The Mean of the Sample Means and the Pooled Standard $\bar { x }$