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# establish knock down factor with R=99% and confidence level=95% for fatigue mean data?

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## establish knock down factor with R=99% and confidence level=95% for fatigue mean data?

(OP)
To all

What is the knock down factor I need to apply to a mean stress to get reliability = 99% with a confidence level = 95%?
I am mixing up my basic stat an need a refresher on this one!

Assume I have a sample size n = 1 (only going to test the system once!)

Thanks
Regards

### RE: establish knock down factor with R=99% and confidence level=95% for fatigue mean data?

Suggest reading the MMPDS data analysis chapter.

But with one specimen, you have insufficient data to estimate the fatigue scatter, so no way to calculate statistical lower bound.

### RE: establish knock down factor with R=99% and confidence level=95% for fatigue mean data?

(OP)
I am reading it and using a set of data/curve from MMPDS as a 1st pass
I am trying to see what (statistical) parameters I need to know if I have 2 points (log-log)r and "correct" for say reliability = 99% with a confidence level = 95%.
Realised that stating n=1 was misleading. I meant to state that I will only test 1-off structure.

Basic stat states standard error = sd/sqrt(n)(sd = standard deviation, n is the number of test specimen used for SN data gathering). This is stated in the MMPDS data but never in generic textbook

so if I have SE = Standard Error of log(N)
correction of the curve would be
Log (N99%) = Log(Nmean)+SE*SD where SD = -3

I think I am getting confused between reliability and confidence level

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