# How to calculate risk for 8 special causes test

Six Sigma – iSixSigma Forums Old Forums General How to calculate risk for 8 special causes test

This topic contains 2 replies, has 2 voices, and was last updated by  hk 13 years, 8 months ago.

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• #42496

hk
Participant

I am looking for the formula to calculate the 8 special causes test in control chart, especially these 2 tests:
6 POINTS IN A ROW ALL INCREASING OR DESCREASING
14 POINTS IN A ROW, ALTERNATIING UP AND DOWN
Is there any web site has any explanation on how to calcualte?

0
#134162

AT
Participant

Hi, I hope that you are going to use the X bar & R chart;
plz. use the Minitab software in the following path:
StatControl ChartsXbar-Rchartoptions —–> there you can find the options for these 8 tests.
Regards,
H.Ramesh.

0
#134164

hk
Participant

Dear Ramesh
Sorry, I think I miss out some word.
I am looking for a formula to calculate the alpha and beta risk for the 8 test. Especially:
14 points alternating up and down
6 points increasing or descreasing.
Example: Test 1, any point out of 3 sigma, we know is 0.135% each side = 0.27% for alpha risk.