Question (Quality Control):
Ten samples of size four were taken from a process, and their weights measured. The sample averages and sample ranges are in the following table. Construct and plot an X-bar and R-chart using these data. Is the process in control?
|
Sample
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
10
|
|
Mean
|
20.01
|
19.98
|
20.25
|
19.9
|
20.35
|
19.23
|
20.01
|
19.98
|
20.56
|
19.97
|
|
Range
|
0.45
|
0.67
|
0.3
|
0.3
|
0.36
|
0.49
|
0.53
|
0.4
|
0.95
|
0.79
|