np Chart
- Last UpdatedMar 19, 2016
- 2 minute read
The following table contains the formulas used to calculate LCL and UCL for a chart point.
The example in the table illustrates the control limits calculated for a sample size of 15.
|
Formula |
Example |
|---|---|
|
CL = LCL = CL – (3 * UCL = CL + (3 * where n is the actual sample size from the sample. If LCL < 0, then LCL = 0; otherwise LCL |
CL = 0.17647 * 15 = 2.64706 LCL = 2.64706 – (3 * = –1.78232 LCL = 0 UCL = 2.64706 + (3 * = 7.07644 |
The following table shows example control limits calculated for each chart point.
|
Label |
Chart Point (Count) |
Size |
LCL |
CL |
UCL |
Lower σ |
Upper σ |
|---|---|---|---|---|---|---|---|
|
1 |
2 |
15 |
0 |
2.647059 |
7.076435 |
0.882353 |
1.47645867 |
|
2 |
1 |
9 |
0 |
1.588235 |
5.019215 |
0.5294117 |
1.14366 |
|
3 |
3 |
15 |
0 |
2.647059 |
7.076435 |
0.882353 |
1.47645867 |
|
4 |
1 |
15 |
0 |
2.647059 |
7.076435 |
0.882353 |
1.47645867 |
|
5 |
4 |
15 |
0 |
2.647059 |
7.076435 |
0.882353 |
1.47645867 |
|
6 |
6 |
20 |
0 |
3.529412 |
8.6440153 |
1.176470 |
1.70486785 |
|
7 |
1 |
15 |
0 |
2.647059 |
7.076435 |
0.882353 |
1.47645867 |
|
8 |
3 |
15 |
0 |
2.647059 |
7.076435 |
0.882353 |
1.47645867 |