Statistical Tolerance

[amitpaul713]

Hi,

I want to have a good understanding on Statistical tolerances and the sigma consideration. Can any one refer me a good link for a website? Thanks in advance

Regards,
Amit Paul

 

[KENAT]

There are plenty of articles and links out there, what particularly are you looking to better understand.

https://www.google.com/search?q=rss+tolerance+stack+up+method&ie=utf-8&oe=utf-8

(Oh, and if you find a reasonable approach to applying statistical methods to mating hole patterns with position tolerance I'd be interested.)

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[amitpaul713]

Hi Kenat,

Thanks for your reply. I am specifically looking for the application of process capability and CPk and based on what are they applied. I understand till RSS but after that I don't understand why they use sigma values i.e rss multiplied by 6sigma/3sigma.

Regards,
Amit Paul

 

[3DDave]

You need to study statistics first. These tell how to make observations about items in the population of interest and from those observations create/use appropriate models in order to make predictions about combinations of those and other items that you have statistical knowledge about.

Until you know how statistics works, you won't understand how to use it for dimensioning and tolerancing.

 

[3DDave]

Kenat,

What about hole patterns is of interest? If you can describe the problem in geometry and measurement terms then at least you can apply Monte Carlo analysis to approximate the distribution and then use any of a variety of packages to estimate the difference between the ones from the Monte Carlo and any formal distribution to see if one of them is a good approximation.

Or, as my useless Statistics prof suggested in an introductory course, depend on your experience. (Because if I had experience why would I be taking this course?)