I hate group therapy sessions!
9th Waste in Lean should be = Actions/ Outcomes from "Group therapy sessions"of sizes larger than 10 with a unusual and misdirected sense of urgency!!!
Wednesday, 9 February 2011
MSA - One Operator
I was quite convinced that MSA of a metric measurement can't be done if you have only one operator! I was almost aghast at the thought of it ...
Only to discover -
Even if you only have one operator (usually) you'll still want to understand the typical variability between operators, unless, of course, your current operator is going to be forced to do that same job FOREVER.
If you still want to use MINITAB with just ONE operator you can use the General Linear Model tool to do the analysis.
Enter the column containing the measurments in the Response field, and enter the column identifying the different parts into the BOTH the Model and Random factors fields. Make sure you click on the Results button and select the "Display expected mean squares..." option.
At the bottom of the output you'll see "Variance Components" listed for the parts column and for "Error". The latter item relates to repeatability. These values are variances.
The Total variance is calculated as
TotalVar=PartVar + ErrorVar
The Repeatability and R&R variance is equal to the ErrorVar since there is no reproducability, nor is there the interaction between operators and parts.
Take the square root of each of these to get the respective Total, Part, and Repeatability (R&R) standard devations.
Multiply each of the stanard deviations by 5.15 to get TV, PV, and EV, respectively.
Obtain the %Study Variations by dividing PV and EV by TV. Multiply by 100 to get a % value. The resulting 100*EV/TV is the %R&R value of interest to most. This value should be less than 10%
If you divide each of the variances by the respective TotalVar you'll get the % Contribution that MINITAB outputs. They are 100*PartVar/TotalVar and 100*ErrorVar/TotalVar.
If you still want to use MINITAB with just ONE operator you can use the General Linear Model tool to do the analysis.
Enter the column containing the measurments in the Response field, and enter the column identifying the different parts into the BOTH the Model and Random factors fields. Make sure you click on the Results button and select the "Display expected mean squares..." option.
At the bottom of the output you'll see "Variance Components" listed for the parts column and for "Error". The latter item relates to repeatability. These values are variances.
The Total variance is calculated as
TotalVar=PartVar + ErrorVar
The Repeatability and R&R variance is equal to the ErrorVar since there is no reproducability, nor is there the interaction between operators and parts.
Take the square root of each of these to get the respective Total, Part, and Repeatability (R&R) standard devations.
Multiply each of the stanard deviations by 5.15 to get TV, PV, and EV, respectively.
Obtain the %Study Variations by dividing PV and EV by TV. Multiply by 100 to get a % value. The resulting 100*EV/TV is the %R&R value of interest to most. This value should be less than 10%
If you divide each of the variances by the respective TotalVar you'll get the % Contribution that MINITAB outputs. They are 100*PartVar/TotalVar and 100*ErrorVar/TotalVar.
I promise to try this out and publish what I get
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