A lumber company makes plywood for commercial construction. A key quality measure is the thickness of the plywood. Every two hours, five pieces of plywood (n = 5) are selected, and the thicknesses are measured.
The data (in inches) for the first 20 samples are as follows:
|
Two-Hour Period
|
Plywood 1
|
Plywood 2
|
Plywood 3
|
Plywood 4
|
Plywood 5
|
|
1
|
0.642
|
0.612
|
0.659
|
0.691
|
0.689
|
|
2
|
0.705
|
0.584
|
0.644
|
0.685
|
0.618
|
|
3
|
0.63
|
0.599
|
0.594
|
0.621
|
0.628
|
|
4
|
0.586
|
0.634
|
0.639
|
0.656
|
0.64
|
|
5
|
0.641
|
0.64
|
0.693
|
0.649
|
0.646
|
|
6
|
0.636
|
0.713
|
0.678
|
0.725
|
0.631
|
|
7
|
0.703
|
0.602
|
0.668
|
0.679
|
0.711
|
|
8
|
0.649
|
0.635
|
0.672
|
0.64
|
0.675
|
|
9
|
0.607
|
0.625
|
0.604
|
0.64
|
0.65
|
|
10
|
0.652
|
0.641
|
0.72
|
0.597
|
0.629
|
|
11
|
0.572
|
0.696
|
0.612
|
0.631
|
0.675
|
|
12
|
0.666
|
0.679
|
0.67
|
0.609
|
0.617
|
|
13
|
0.673
|
0.662
|
0.622
|
0.644
|
0.656
|
|
14
|
0.669
|
0.656
|
0.623
|
0.71
|
0.667
|
|
15
|
0.654
|
0.677
|
0.678
|
0.632
|
0.623
|
|
16
|
0.686
|
0.614
|
0.603
|
0.674
|
0.671
|
|
17
|
0.72
|
0.696
|
0.692
|
0.655
|
0.652
|
|
18
|
0.666
|
0.651
|
0.619
|
0.596
|
0.677
|
|
19
|
0.665
|
0.671
|
0.658
|
0.62
|
0.69
|
|
20
|
0.642
|
0.625
|
0.626
|
0.638
|
0.637
|
a. develop an x chart to determine if the process is stable or not.
b. develop an R chart to determine if the process is stable or not.