How do calulate nicety reference value by Pa value in Attribute Analytic Method of MSA? :whip:

I am bouncing this to the top as there has been a lot of discussion about attribute GRR and I have also been asked about it offline.
I am at a loss to understand where this comes form and I cannot see where in the example posted it is in fact used
Attribute - short & long 2005 06 20 example.xls (http://elsmar.com/Forums/attachment.php?attachmentid=3702&d=1119272985) in this thread Ford Specific Attribute Gage Study - 50 samples, 3 trials, 3 ops - Spreadsheet Wanted (http://elsmar.com/Forums/showthread.php?t=10710)
Any one:frust:

I am at a loss to understand where this comes form and I cannot see where in the example posted it is in fact used


At a loss to see where what comes from? Unfortunately, learner's meaning was lost somewhere in translation; if you know what he was asking please share it with us, and maybe we can help.

OK,
Page 127 of the MSA book has a table that is reproduced in the link that I pointed to,.
How is the number for the column Reference calculated and where is it used in the calculations afterwards.

OK,
Page 127 of the MSA book has a table that is reproduced in the link that I pointed to,.
How is the number for the column Reference calculated and where is it used in the calculations afterwards.

I'm still clueless as to how you extracted that question from the original post, but does the paragraph at the top of page 128 help?

Ok, I am clueless as well. For some reason I am a total blank on this:(
I see that I was confused between the 2 systems, so I will now ask about the risk method.
I was off topic:bonk:
Let me try to make sense of this and hope that you bear with me.
The table on P127 has a column Ref Value which according to P128 were not initially determined.
I cannot see any way in which the Ref value is calculated and what use it is please show me the light:(

The reference values on page 127 are not calculated ones.
They have been measured with a variable measuring system.
This is explained on page 129 (near the end of the page)

Best regards,

Antoine

Thank you:agree1:

The question is about Attribute Analytic Study that is covered on Page 135-140 in the manual.

You take the parts and have an operator test them 20 times each. Depending on the no of accepts, the manual gives rules to calculate the Probability of Acceptance (P'a). These can be a little confusing but not difficult if you read carefully.

How do calulate nicety reference value by Pa value in Attribute Analytic Method of MSA? :whip:For the purpose of calculating Bias, you need to find out the Reference value corresponding to Probability of acceptance P'a=0.5. For this you plot the points (P'a on Y axis and Measured values on X axis) on a normal probability plot, plot the regression line and simply substitute 0.5 for the Y term in the equation of the line to get the corresponding X value. Use this as the reference value in the equation for calculating bias.

Simple.... no? ;) :nope: