S6.11 Twelve samples each containing five parts were taken from a proces

S6.11

Twelve samples each containing five parts were taken

from a process that produces steel rods. The length of each rod in the

samples was determined. The results were tabulated and sample

means and ranges were computed. The results were:

Sample Sample Mean (in.) Range (in.)

1 10.002 0.011

2 10.002 0.014

3 9.991 0.007

4 10.006 0.022

5 9.997 0.013

6 9.999 0.012

7 10.001 0.008

8 10.005 0.013

9 9.995 0.004

10 10.001 0.011

11 10.001 0.014

12 10.006 0.009

a) Determine the upper and lower control limits and the overall

means for -charts and R-charts.

b) Draw the charts and plot the values of the sample means and

ranges.

c) Do the data indicate a process that is in control?

d) Why or why not