P/T ratio equivalent for one sided spec??
Message posted by PMH (via 194.106.141.243) on November 2, 2001 at 7:45 AM (ET)

Hi all,

I need to perform a Gage R&R study on test equipment for a product that has a one-sided spec. I can't present the results as a P/T ratio. What is the equivalent for a single sided spec?? and what are the standards for judging it e.g. >30% for a P/T ratio??

Any help would be greatly appreciated?

READERS RESPOND:
(In chronological order. Most recent at the bottom.)

Re: P/T ratio equivalent for one sided spec??
Message posted by PMH (via 194.106.141.243) on November 6, 2001 at 12:06 PM (ET)

Can somebody help please. If the question doesn't make sense or is nonsense, please let me know.

Thanking You,
Paul

Re: P/T ratio equivalent for one sided spec??
Message posted by Phil (via 66.32.156.250) on November 7, 2001 at 11:52 AM (ET)

What if instead of using the specification tolerance in the denominator, you use the natural tolerance of the process (six sigma of the actual process variation). Then you will have a number that indicates the quality of the measurement system in the same way as the P/T ratio intended. I would think that if the P/T ratio computed in this manner was < 0.25 (and the lower the better), you would be considered OK.

Make sure you footnote or explain what you did and why if you include it in a report.

Re: P/T ratio equivalent for one sided spec??
Message posted by PMH (via 194.106.141.243) on November 9, 2001 at 5:28 AM (ET)

Nonsense
Message posted by babaqoy mastan (via 63.59.227.54) on November 19, 2001 at 3:44 PM (ET)

Re: P/T ratio equivalent for one sided spec??
Message posted by PMH (via 194.106.141.243) on November 20, 2001 at 4:36 AM (ET)

Your man above has reminded me of a question I wished to pose to this forum.

I intend to calculate a P/T-like ratio as described by Phil above, i.e. my (Gage capability)/(6 Process Sigma). However, textbooks differ on the manner order of Gage Capability to be used.
Some suggest (Gage capability)/(6 Process Sigma).....
Others suggest (6 Gage Capability)/ (6 Process Sigma).....
While others again suggest (5.15 Gage Capability)/ (6 Process Sigma).

Which is the most commonly used?
The (6...)/(6...) option appeals to me as it would reflect total test varience as a percentage of total process varience. If used does the 25% test criteria as suggested by Phil still stand.

Thanks, Paul.