In: Statistics and Probability
Solve step-by-step the following:
1) X-bar and R control Chart
Subgroup |
X1 |
X2 |
X3 |
X4 |
X-bar |
R |
1 |
1.2 |
1.1 |
1.1 |
2.3 |
||
2 |
3.2 |
1.3 |
1.3 |
3.3 |
||
3 |
1.3 |
1.4 |
1.3 |
1.1 |
||
4 |
3.2 |
1.1 |
3.3 |
2 |
||
5 |
2.1 |
3.2 |
2.4 |
2.3 |
||
6 |
3.1 |
3.1 |
3.2 |
3.3 |
||
7 |
3 |
1 |
2.2 |
2.1 |
||
8 |
2.3 |
1.3 |
3.1 |
2.4 |
||
9 |
4 |
3.3 |
4 |
4.3 |
||
10 |
1.2 |
3.1 |
1.3 |
1.3 |
||
11 |
2.2 |
1.4 |
1.1 |
3 |
||
12 |
3.2 |
2.3 |
3.1 |
1.2 |
||
13 |
1.1 |
3 |
1 |
3.1 |
||
14 |
3.1 |
1.3 |
2.2 |
1.2 |
||
15 |
2.3 |
2 |
1 |
2.3 |
||
16 |
2.2 |
3.1 |
3.4 |
3.2 |
||
17 |
1.2 |
1.2 |
2.1 |
2 |
||
18 |
1.3 |
3.3 |
1.2 |
2.1 |
||
19 |
2.2 |
2 |
1.3 |
3 |
||
20 |
0.7 |
1.1 |
1.1 |
1.2 |
||
21 |
3 |
3.1 |
2.2 |
2.2 |
||
22 |
2.3 |
2.3 |
3.1 |
2.2 |
||
23 |
2.3 |
1.3 |
1.2 |
3.1 |
||
24 |
3.1 |
3 |
1.4 |
1.4 |
||
25 |
3.1 |
3.2 |
2.1 |
2.1 |
a. Determine the Trial UCL, CL, and LCL for both charts of X-bar and R
b. Determine the Revised UCL, CL, and LCL for both charts of X-bar and R
a) The control limits for X-bar chart is,
UCL= (X-bar) + A2 R = 2.400151
CL = X-bar = 2.1701
LCL = (X-bar) - A2 R = 1.940049
Where A2 is table value corresponding to n = 25
The control limits for R chart is
UCL = D3 R = 2.317048
CL = R = 1.5036
LCL = D4 R = 0.690192
Where D3 & D4 is table value corresponding to n = 25.
A2 = 0.153, D3 = 0.459, D4 = 1.541
Sub group | x1 | x2 | x3 | x4 | X bar | R |
1 | 1.2 | 1.1 | 1.1 | 2.3 | 1.425 | 1.2 |
2 | 3.2 | 1.3 | 1.3 | 3.3 | 2.275 | 2 |
3 | 1.3 | 1.4 | 1.3 | 1.1 | 1.275 | 0.3 |
4 | 3.2 | 1.1 | 3.3 | 2 | 2.4 | 2.2 |
5 | 2.1 | 3.2 | 2.4 | 2.3 | 2.5 | 1.1 |
6 | 3.1 | 3.1 | 3.2 | 3.3 | 3.175 | 0.2 |
7 | 3 | 1 | 2.2 | 2.1 | 2.075 | 2 |
8 | 2.3 | 1.3 | 3.1 | 2.4 | 2.275 | 1.8 |
9 | 4 | 3.3 | 4 | 4.3 | 3.9 | 1 |
10 | 1.2 | 3.1 | 1.3 | 1.3 | 1.725 | 1.9 |
11 | 2.2 | 1.4 | 1.1 | 3 | 1.925 | 1.9 |
12 | 3.2 | 2.3 | 3.1 | 1.2 | 2.45 | 2 |
13 | 1.1 | 3 | 1 | 3.1 | 2.05 | 2.1 |
14 | 3.1 | 1.3 | 2.2 | 1.2 | 1.95 | 1.9 |
15 | 2.3 | 2 | 1 | 2.3 | 1.9 | 1.3 |
16 | 2.2 | 3.1 | 3.4 | 3.2 | 2.975 | 1.2 |
17 | 1.2 | 1.2 | 2.1 | 2 | 1.625 | 0.9 |
18 | 1.3 | 3.3 | 1.2 | 2.1 | 1.975 | 2.1 |
19 | 2.2 | 2 | 1.3 | 3 | 2.125 | 1.7 |
20 | 0.7 | 1.1 | 1.1 | 1.2 | 1.025 | 0.5 |
21 | 3 | 0.31 | 2.2 | 2.2 | 1.9275 | 2.69 |
22 | 2.3 | 2.3 | 3.1 | 2.2 | 2.475 | 0.9 |
23 | 2.3 | 1.3 | 1.2 | 3.1 | 1.975 | 1.9 |
24 | 3.1 | 3 | 1.4 | 1.4 | 2.225 | 1.7 |
25 | 3.1 | 3.2 | 2.1 | 2.1 | 2.625 | 1.1 |
Average | 2.1701 | 1.5036 |
From above graph we see that the process of X-bar chart and R chart is out of control because in both of graph we see that some points goes above UCL line and some points are below LCL line.
b) We see that the process of X-bar and R chart is out of control. Hence we revised control limits of X-bar and R chart.
For revising control limits we delete the points which are above UCL line and below LCL line in both X-bar and R chart and again compute control limits for both of these chart hence we get revised control limits.
Sub group | x1 | x2 | x3 | x4 | X bar | R |
1 | 3.2 | 1.3 | 1.3 | 3.3 | 2.275 | 2 |
2 | 3.2 | 1.1 | 3.3 | 2 | 2.4 | 2.2 |
3 | 3 | 1 | 2.2 | 2.1 | 2.075 | 2 |
4 | 2.3 | 1.3 | 3.1 | 2.4 | 2.275 | 1.8 |
5 | 1.2 | 3.1 | 1.3 | 1.3 | 1.725 | 1.9 |
6 | 2.2 | 1.4 | 1.1 | 3 | 1.925 | 1.9 |
7 | 3.2 | 2.3 | 3.1 | 1.2 | 2.45 | 2 |
8 | 1.1 | 3 | 1 | 3.1 | 2.05 | 2.1 |
9 | 3.1 | 1.3 | 2.2 | 1.2 | 1.95 | 1.9 |
10 | 2.3 | 2 | 1 | 2.3 | 1.9 | 1.3 |
11 | 1.3 | 3.3 | 1.2 | 2.1 | 1.975 | 2.1 |
12 | 2.2 | 2 | 1.3 | 3 | 2.125 | 1.7 |
13 | 3 | 0.31 | 2.2 | 2.2 | 1.9275 | 2.69 |
14 | 2.3 | 2.3 | 3.1 | 2.2 | 2.475 | 0.9 |
15 | 2.3 | 1.3 | 1.2 | 3.1 | 1.975 | 1.9 |
16 | 3.1 | 3 | 1.4 | 1.4 | 2.225 | 1.7 |
Average | 2.107969 | 1.880625 |
table values corresponding to n = 16 is,
A2 = 0.212, D3 = 0.363, D4 = 1.637
The revised control limits for X-bar chart is,
UCL= (X-bar) + A2 R = 2.50662
CL = X-bar = 2.107969
LCL = (X-bar) - A2 R = 1.709277
The revised control limits for R chart is
UCL = D3 R = 3.078583
CL = R = 1.880625
LCL = D4 R = 0.870729