Strange PT Ratio on an Excel spreadsheet for variable GRR ANOVA Method

[stefano.larghi]

Hi to everybody.

I've got from a customer an Excel spreadsheet for variable GRR ANOVA Method.

It shows, between many known indexes, a value quite strange: that is in "gage results" it compares:
sigmaRR vs design tolerances (named IT) / 27.

Clearly it belongs (it seems to me) to a P/T ratio family, but I can't understand the factor 27.

Would it be :
a) 6*sigmaRR vs IT/4.5
b) 4,5 *sigmaRR vs IT/6

but why are using different sigma spread coefficients (6 and 4,5)?
Usually P/T = 6*sigmaRR / IT
Does anybody managed it?
thanks

 

[NumberCruncher]

Hi Stefano

Try asking your customer. Someone put it in, presumably they had a reason.

NC

 

[stefano.larghi]

Thanks NC! I thought so but before I wanted to check any missing concept in my reasoning (about indexes or acceptability criteria).
bye