Page 218 - DMGT524_TOTAL_QUALITY_MANAGEMENT

Unit 14: Statistical Process Control

Grand Mean Notes

Let the sample mean for the ith sample be X . Then we estimate the mean of the population, μ,
i
by the grand mean:
1 m
X = ∑ X i
i1
m =
Average Range and Estimator of σ

Let R be the range of the ith sample, and let
i
1 m
R = ∑ R i
i1
m =
be the average. Then R is an estimator of μ and an estimator of σ is:
R
R
ˆ σ =
d
2
The X Control Chart

The center line and upper and lower control limits for an X control chart are:

+
UCL = xA r
2
CL = x
LCL = xA r− 2
where the constant A is tabulated for various sample sizes in Appendix Table of Control Charts.
2
Figure 14.12: Control Chart

Target

Lower warning line

1 2 3 4 5
Sample Number

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