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• #49496

walden
Participant

Im stumped on finding the upper and lower control limits using 2 sigma limits and deciding what chart to use. All that is given is the product number then the number of defects per product…
product#1=7 defects, 2=4,3=3,4=5,5=6,6=3,7=8,8=2, 9=7,10=2,11=3

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#169198

Savage
Participant

You might consider a c-chart. The standard method of computing the control limits will be at +/- 3 sigma, not 2, but you can adjust for this.

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#169202

Ron
Member

Shewhart control charts use an approximation methodolgy to calculate the upper and lower control limits. each type of chart has it’s own unique formula for calculating th SD approximation.
Don’t try using SD from other than the proper formula for the specific chart you are trying to chart.

The one you are looking for could be a C chart, a U chart or an ImR
depending on the particulars.

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#169204

walden
Participant

Thanks. I guess I will use the c chart method and find the ucl and lcl. I was a little confused because all of the previous scenarios I came across mentioned a sample size and  this one had limited information. Plus this scenario used the 2 sigma instead of standard 3.

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#169206

SiggySig
Member

Chris,
Out of curiosity, what is the application of 2 sigma control limits? Messing with control limits can have some pretty disastrous consequences…

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Viewing 5 posts - 1 through 5 (of 5 total)

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