How to use ±3 sigma control limits in JMP charts
Last Modified: Jan 20, 2020 2:48 AM
JMP The main way to create a control chart in Control Chart Builder no see .properties of data ( continuous / categorical, etc. ) If you specify correctly JMP automatically creates a control chart in .
but , One thing you need to know is that JMP The control limits provided by 3 Not a sigma control limit . JMP The management limits provided by Moving Range We provide management limits according to ( Please refer to the link below ).
Control Limits for Individual Measurement and Moving Range Charts
In fact, one of the questions that many people ask is why default which is given as data of sample standard deviation (s) use ( i.e. ± 3 Use of sigma control limits ) without doing Moving Range It is whether to obtain the control limit from .
this is , It would be good to note that the reason is .
- When the first control chart was actually developed (1920 years Bell in the lab Walter A. Shewhart invented by ), While managing a lot of data manually chart and , Each representative value ( Average / dispersion, etc. ) It was difficult to obtain by hand . 1920 In the 1980s, there were no computers or even calculators. It's time .
- In addition sample standard deviation Finding the sigma control limit by using it is assuming the normality of the data. , Actual control chart data time-dependent Therefore, it is difficult to say that normality is satisfied. .
- For the same reason as above moving range Estimates obtained using ( Convenience of calculations & No need to make distribution assumptions robust box ).
However , must be ± 3 If you want to draw a sigma control limit, you can use the following method. . example is JMP Sample Data Table sign Diameter (Sample Data middle Quality Control is in the folder ) I will show you as an example .
open the data , Please select the menu as follows .
Analyze >> Quality and Process >> Control Chart >> I/MR Control Chart
When the following dialog box appears Diameter cast Y select on
The control chart below is mentioned Moving Range This is the result showing the management limit of . To change this part, click the red circle in the upper left corner of the figure below. Red Triangle select Show Control Panel Please select the menu .
When the Control Panel appears, Limits A selection box will appear where you can set .
from below Levey Jennings Please select .
The final result is below . as you can see Levey Jennings Management limits were set using the method , The method is looking for ± 3 sigma It is a management limit. . Levey Jennings Please refer to the link below for this .
This post originally written in Korean and has been translated for your convenience. When you reply, it will also be translated back to Korean.
Comments