A Peachfarm Internet Property

The Cove Business Standards Discussion Forums More Free Files Forum Discussion Thread Post Attachments Listing Cove Discussion Forums Main Page
UL - Underwriters Laboratories - Health Sciences
Go Back   The Elsmar Cove Business Systems and Standards Discussion Forums > Common Quality Assurance Processes and Tools > General Metrology, Measurement Device, Calibration and Test Laboratories > Gage R&R (GR&R) and MSA (Measurement Systems Analysis)
Forum Username

Elsmar Cove Forum Visitor Notice(s)

Wooden Line

Process Variation and Total Variation - Relationship and Definitions


Elsmar XML RSS Feed
Elsmar Cove Forum RSS Feed

Monitor the Elsmar Forum
Sponsor Links



Courtesy Quick Links

Links that Cove visitors will find useful in your quest for knowledge:


International Standards Bodies - World Wide Standards Bodies

ASQ - American Society for Quality

International Standards Organization - ISO Standards and Information

Atul's
Quality Forum Online

Howard's
International Quality Services

Marcelo Antunes'
SQR Consulting, and
Medical Devices Expert Forum

Bob Doering
Bob Doering's Blogs and,
Correct SPC - Precision Machining

NIST's Engineering Statistics Handbook

IRCA - International Register of Certified Auditors

SAE - Society of Automotive Engineers

Quality Digest

IEST - Institute of Environmental Sciences and Technology


Related Topic Tags
total variation, definitions, variation (measurement), processes (general), differences (general)
Reply
 
Thread Tools Search this Thread Rating: Thread Rating: 1 votes, 5.00 average. Display Modes
  Post Number #1  
Old 16th July 2007, 12:16 AM
9876543219

 
 
Total Posts: 4
Question Process Variation and Total Variation - Relationship and Definitions

hi,everyone ,who could show me the correlation of process variation and total variation ,and what's the definition of process variation thank you

Last edited by 9876543219; 16th July 2007 at 01:12 AM.

Sponsored Links
  Post Number #2  
Old 16th July 2007, 02:04 AM
harry

 
 
Total Posts: 6,273
Re: the relation between process variation and total variation

Quote:
In Reply to Parent Post by 9876543219 View Post

hi,everyone ,who could show me the correlation of process variation and total variation ,and what's the definition of process variation thank you
Welcome my friend. I noticed that you are already searching for information on your own - that's very good.

Pending replies from fellow Covers who are well versed in this subject, perhaps you would like to look at this thread and other links contain therein.

Have a good time here.
Sponsored Links

  Post Number #3  
Old 16th July 2007, 01:30 PM
Miner's Avatar
Miner

 
 
Total Posts: 3,846
Re: Relationship between Process Variation and Total Variation

Quote:
In Reply to Parent Post by 9876543219 View Post

hi,everyone ,who could show me the correlation of process variation and total variation ,and what's the definition of process variation thank you
[StdDev(total variation)]^2 = [StdDev(process variation)]^2 + [StdDev(repeatability)]^2 + [StdDev(reproducibility)]^2 + ...

^2 means "squared"
StdDev(xxxxxx) means the standard deviation of (xxxxxx)

Standard deviations cannot be added, the variance (StdDev^2) can be added.

I have seen PT variously interpreted as Part Variation or Process Variation. It is the variation of the parts used in the MSA. Ideally, the variation of these Parts equals the variation of the Process that they came from, so Part Variation should equal Process Variation.
  Post Number #4  
Old 17th July 2007, 12:16 AM
9876543219

 
 
Total Posts: 4
Re: Relationship between Process Variation and Total Variation

fisrt of all ,i getta say thanks to you all moderators for your replies ,your answers has kind of enlightened me .
yeah, that's what got me confused ,i don't know the exact formula for Total variation , so is the total variation equal to the sum of the three items ,and what does the dots behind mean? is there any more items shall be added to the previous ones ?

and from your words i feel may be in some situation the part variation is not equal to process variation ....right ,so that's the key problem casting me into confusion ......
is that all that i should concern ,i mean the total variation = deviation from process +deviation from measurement system ? and the process variation ideally equals part variation (sometimes at least we should consider the effects from ambience right ?) and the measurement system consists of only two parts : repeatability and reproducibility ?

i appreciate very much ..........
  Post Number #5  
Old 17th July 2007, 03:15 AM
antoine.dias's Avatar
antoine.dias

 
 
Total Posts: 512
Re: Relationship between Process Variation and Total Variation

In the MSA study it is best that parts chosen for the study represent the process.
Keeping this in mind it is very important how you collect the samples for the study.
Like Miner said the variation of the chosen parts should represent the process variation.
A lot of mistakes are made when samples are collected and people just grab 10 pcs from the machine shop to be used in the study. Result is: not enough variation in the parts, resulting in high percentage of EV and AV in relation to the calculated TV together with a very low ndc.

So take care to choose the right samples.

Best regards,

Antoine
  Post Number #6  
Old 17th July 2007, 07:39 AM
Miner's Avatar
Miner

 
 
Total Posts: 3,846
Re: Relationship between Process Variation and Total Variation

Quote:
In Reply to Parent Post by 9876543219 View Post

fisrt of all ,i getta say thanks to you all moderators for your replies ,your answers has kind of enlightened me .
yeah, that's what got me confused ,i don't know the exact formula for Total variation , so is the total variation equal to the sum of the three items ,and what does the dots behind mean? is there any more items shall be added to the previous ones ?

and from your words i feel may be in some situation the part variation is not equal to process variation ....right ,so that's the key problem casting me into confusion ......
is that all that i should concern ,i mean the total variation = deviation from process +deviation from measurement system ? and the process variation ideally equals part variation (sometimes at least we should consider the effects from ambience right ?) and the measurement system consists of only two parts : repeatability and reproducibility ?

i appreciate very much ..........
The dots mean that there are other terms that might be added if significant such as an operator x part interaction. This sometimes is a significant part of measurement error, but not always. The ANOVA method breaks it out separately, and the Range method includes it in Repeatability.

The post after your question about part and process variation aswered this nicely.

The measurement system also includes Bias, Linearity and Stability, which includes the effects of ambient conditions.
  Post Number #7  
Old 24th July 2007, 01:56 AM
9876543219

 
 
Total Posts: 4
Let Me Help You Re: Relationship between Process Variation and Total Variation

hi miner ,today i get the formula in MSA handbookTV= process variation/6 (page 116 of MSA manual)as you've listed a formua quoting : [StdDev(total variation)]^2 = [StdDev(process variation)]^2 + [StdDev(repeatability)]^2 + [StdDev(reproducibility)]^2 + ...
so don't you think these two are kind of contradictory of each other
i am new in this field , and easy to get confused ...... thank you

Last edited by 9876543219; 24th July 2007 at 07:50 AM.
  Post Number #8  
Old 24th July 2007, 09:41 AM
Miner's Avatar
Miner

 
 
Total Posts: 3,846
Re: Relationship between Process Variation and Total Variation

Quote:
In Reply to Parent Post by 9876543219 View Post

hi miner ,today i get the formula in MSA handbookTV= process variation/6 (page 116 of MSA manual)as you've listed a formua quoting : [StdDev(total variation)]^2 = [StdDev(process variation)]^2 + [StdDev(repeatability)]^2 + [StdDev(reproducibility)]^2 + ...
so don't you think these two are kind of contradictory of each other
i am new in this field , and easy to get confused ...... thank you
These equations are not really in disagreement. The MSA process actually calculates these various components separately, so that you do not see the equation that I provided at one time. However, the MSA calculations are indeed based on this formula.
Reply

Lower Navigation Bar
Go Back   The Elsmar Cove Business Systems and Standards Discussion Forums > Common Quality Assurance Processes and Tools > General Metrology, Measurement Device, Calibration and Test Laboratories > Gage R&R (GR&R) and MSA (Measurement Systems Analysis)

Bookmarks



Visitors Currently Viewing this Thread: 1 (0 Registered Visitors (Members) and 1 Unregistered Guest Visitors)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Forum Search
Display Modes Rate Thread Content
Rate Thread Content:

Forum Posting Settings
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Similar Discussion Threads
Discussion Thread Title Thread Starter Forum Replies Last Post or Poll Vote
Ppk & Cpk - Within Subgroup Variation is always smaller than Total Variation Stevenli Capability, Accuracy and Stability - Processes, Machines, etc. 18 12th February 2014 12:31 AM
Incoming Source of Variation & Source of Variation in Process Flow Chart manojdparab TS 16949 - International Automotive Quality Systems Standard 3 27th August 2011 02:54 PM
Total Tolerance Method vs. Total Variation Method - Measurement System Analysis ram4302 Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1 11th July 2010 01:16 PM
How to use Total Variation based on Process or Tolerance? Page 60 of the MSA manual Frestruc Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2 2nd May 2006 03:28 AM
Gage R&R - Tolerance vs. Total Variation - Process Variation vs. Gage Variation Jrodrigu Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2 29th August 2002 08:09 AM



The time now is 09:20 AM. All times are GMT -4.
Your time zone can be changed in your UserCP --> Options.


 


NOTE: This forum uses "Cookies" -- The Elsmar Cove is *Copyright Free*.
A Peachfarm Internet Property