Confidence & Reliability - Reference to a 90/95 Confidence & Reliability Level

[username]

Re: Confidence and Reliability - Reference to a 90/95 confidence and reliability leve

Miner, Thanks for the formula. Its great!
Do you have something similar for variable data?

 

[Miner]

Re: Confidence and Reliability - Reference to a 90/95 confidence and reliability leve

Here is a link to a Weibayes based sample size formula for a reliability demonstration test.

 

[Josielyn]

Re: Confidence and Reliability - Reference to a 90/95 confidence and reliability leve

Thank you for the formula. It is very useful. However, what test time should I use for this sample size? The requirement is to demonstrate 98% reliability with 90% confidence 3 years after shipment when used in the defined environments and subjected to 8500 on-off power cycles per year.

 

[k9thunder]

Re: Confidence and Reliability - Reference to a 90/95 confidence and reliability leve

Many thanks to Miner for the attribute Excel SS!

 

[Sam Lazzara]

Re: Confidence and Reliability - Reference to a 90/95 confidence and reliability leve

Here is an excerpt from a document that I prepared that has tables for attribute data confidence and reliability for 0, 1, 2 and 3 failures allowed in the sample, and basic methodology for analyzing variables data to determine upper and lower statistical limits (confidence/reliability analysis).

References are cited below the attribute data tables. They are:
“Reliability Statistics” by R. Dovich (1990; ASQ Press)
F-tables per “Reliability Mathematics” by B.L. Amstadter (1971; McGraw-Hill)

 

[Roscoe Splevins]

Re: Confidence and Reliability - Reference to a 90/95 confidence and reliability leve

Sam,

Excellent chart. I'd like to see more of this procedure. We are involved in a similar situation as that which started this thread. Customer insists on justification of sample plan but has no suggestion as to how. Customer has no internal documented justification control document to reference.

 

[Reliable.Outlier]

Re: Confidence and Reliability - Reference to a 90/95 confidence and reliability leve

Hi everyone,

I think the complete form of the question ask by Josielyn at 31st January 2011, 05:18 AM is still unanswered.

Any answer?

Best regards

Josielyn
31st January 2011, 05:18 AM
Thank you for the formula. It is very useful. However, what test time should I use for this sample size? The requirement is to demonstrate 98% reliability with 90% confidence 3 years after shipment when used in the defined environments and subjected to 8500 on-off power cycles per year.

 

[Miner]

Re: Confidence and Reliability - Reference to a 90/95 confidence and reliability leve

Unfortunately, I missed this post.

The answer to this posters question is to use the test time required to meet the project schedule. The longer the test time available the fewer samples will be required to demonstrate the reliability requirement. The shorter the test time available, the greater the sample size required to demonstrate the same requirement.

 

[Frankli]

Re: Confidence and Reliability - Reference to a 90/95 confidence and reliability leve

what's the mean of reliability and confidence?

 

[Frankli]

Re: Confidence and Reliability - Reference to a 90/95 confidence and reliability leve

Who can help to explain what the confidence level and reliability? thank you very much.