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  Statistical Techniques and 6 Sigma
  MTTR

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Author Topic:   MTTR
Michael Busha
unregistered
posted 12 April 2001 09:48 AM           Edit/Delete Message   Reply w/Quote
Does anyone know a quick and dirty way to calculate MTTR? We have two kinds of solenoid valves, one is ISO rated, the other is not. I want to prove that the MTTR of the ISO rated valve is not significantly different from that of the non ISO rated valve. We have the capability of actually disassembling and reassembling both valves to get an accurate measure. Is there a formula I can plug the values into? Thanks for any help. The results of this analysis could save my company $40,000.

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Marc Smith
Cheech Wizard

Posts: 4119
From:West Chester, OH, USA
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posted 15 April 2001 02:02 AM     Click Here to See the Profile for Marc Smith   Click Here to Email Marc Smith     Edit/Delete Message   Reply w/Quote
I would relate it to MTBF and do an accellerated life test. I don't know how to do MTTRepair.

Can you state the difference between MTBF and MTTR?

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Al Dyer
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Posts: 622
From:Lapeer, MI USA
Registered: Oct 2000

posted 15 April 2001 03:46 PM     Click Here to See the Profile for Al Dyer   Click Here to Email Al Dyer     Edit/Delete Message   Reply w/Quote
Would the data involved be attribute or variable data?

Would also like to know if what you are looking for is Mean Time Between Failure?

We do alot of tool life studies (drills, insers etc...) which is basically MTFB. It's a good tool and can have a quick payback on investment time (cost).

ASD...

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Abe
unregistered
posted 16 April 2001 03:28 AM           Edit/Delete Message   Reply w/Quote
[QUOTE]Originally posted by Michael Busha:
[B]Does anyone know a quick and dirty way to calculate MTTR?

Yes,

a.Take 5 of the ISO valves and 5 of the other type
b. Define significant repair task(s).
c. make the repair task(s)
d. record repair times
e. Make a t-test for sifnificance

Make this test twice with one tecnician repairing ISO velve and one the other one than switch tecnicians and repate

Good luck

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Abe
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posted 16 April 2001 03:37 AM           Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Abe:
[QUOTE]Originally posted by Michael Busha:
[B]Does anyone know a quick and dirty way to calculate MTTR?

Yes,

a.Take 5 of the ISO valves and 5 of the other type
b. Define significant repair task(s).
c. make the repair task(s)
d. record repair times AND CALCULATE THE Mean Time To Repair (MTTR)
e. Make a t-test for sifnificance differance of the means

Make this test twice with one tecnician repairing ISO velve and one the other one than switch tecnicians and repate

Good luck


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Michael Busha
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posted 16 April 2001 07:20 AM           Edit/Delete Message   Reply w/Quote
Thanks Abe. The procedure looks great but, I'm embarrassed to say I cannot find "T-test" in any of my references. Could you elaborate?

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Abe
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posted 16 April 2001 09:48 AM           Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Michael Busha:
Thanks Abe. The procedure looks great but, I'm embarrassed to say I cannot find "T-test" in any of my references. Could you elaborate?

Hi Michael,
T-test is a statistical test of hypothesis that compare two samles and make a statement with some confidence whether the two samples
came from one (No MTTR difference)or two populations (significant MTTR difference).
You may find infronation on this subject in any statistical textbook
If you need more information or help you may email me at avigeva@rada.com

Avi

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Roger Eastin
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From:Greenville, SC
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posted 17 April 2001 08:25 AM     Click Here to See the Profile for Roger Eastin   Click Here to Email Roger Eastin     Edit/Delete Message   Reply w/Quote
Just a thought: Some MTTR data are not normally distributed, so be careful when applying your t-test. Check your data first to determine whether it is normally distributed or not. If it is not,do a transformation (for instance, take the square root of the data) on the data to approximate normality and then do your t-test. This is a typical technique used in designed experiments and it works well.

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Abe
unregistered
posted 23 April 2001 01:29 AM           Edit/Delete Message   Reply w/Quote
Michael,
Please resend me your mail.
The one i have came out wrong so you did not get my answere.
Abe

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