carte de contrôle avec des données qui sont déjà des moyennes
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Created:
Nov 15, 2023 10:50 AM
| Last Modified: Nov 15, 2023 7:50 AM(876 views)
Bonjour
je cherche à indiquer à la plate forme qualité que les données que je récolte sont déjà des moyennes (de 9-21-49 valeurs selon les cas).
je n'ai pas trouvé où indiquer à JMP que les valeurs de la table sont déjà des moyennes. Du coup, les limites calculées sont fausses par rapport à ce que je calcule pour mes données sous Matlab.
Welcome to the community. I'm a little confused by the question. Do you have all of the data or only the averages? If you do not have the complete data set, it is impossible to calculate the range of the within subgroup variation. This is required as the average range is used to calculate control limits for both the range chart and the average chart. Another option is to do an IR chart (Individual moving range). The IR chart is not answering the same question as the X-bar chart.
"All models are wrong, some are useful" G.E.P. Box
When you mentioned the calculated limit not same like in Matlab, what type of method that you used in Matlab to calculate control limit? If you want a flexible calculation of control limit (depending on your scenario), maybe you can use Control Chart Builder. If you just want to add a note to state that the column is average, you can define the column properties & add notes that it is an average ( but i doubt it will change the calculation ). For single data point (in this case “average value”), you can either use IR method or Levey-Jennings in JMP IR in this case will treat your average as single point & sigma is moving range between the 2 averages. Levey-Jennings will treat you average as single point as well & sigma is Levey-Jennings (overall standard deviation of all averages).
p/s: Earlier post mentioned Minitab instead of Matlab. Thanks @ih for the correction.
I am no expert here but I second the question from @WebDesignesCrow about how this is done in MATLAB. The variation of individual samples seems like it would be central to subsequent analyses so I suspect there is some assumption made in MATLAB. Consider the samples data in the example script below. Using the same averages for each group but different variations within the group, the control limits change significantly.
Run this script to recreate the sample data and charts above: