For samples of size 10 each, sample means and ranges were calculated for a process every day for 25 days:
xIˋ¿ = 132.66 R = 12.38
Determine the control limits for the R-chart accurate to 2 decimal places.
Table of Control Chart Constants
Sample Size
A2
D3
D4
2
1.880
0
3.267
3
1.023
0
2.575
4
0.729
0
2.282
5
0.577
0
2.114
6
0.483
0
2.004
7
0.419
0.076
1.924
8
0.373
0.136
1.864
9
0.337
0.184
1.816
10
0.308
0.223
1.777
11
0.285
0.256
1.744
12
0.266
0.283
1.717
13
0.249
0.307
1.693
14
0.235
0.328
1.672
15
0.223
0.347
1.653
16
0.212
0.363
1.637
17
0.203
0.378
1.622
18
0.194
0.391
1.609
19
0.187
0.404
1.596
20
0.180
0.415
1.585
21
0.173
0.425
1.575
22
0.167
0.435
1.565
23
0.162
0.443
1.557
24
0.157
0.452
1.548
25
0.153
0.459
1.541
a) Centreline =
b) LCL = UCL =
c) Can we conclude that the process is out of control based on the following data representing one of the samples selected? Hint: Check if the sample range is within control limits.