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- March 19, 2009 at 8:30 pm #158454
Hello,

I have a hard time in calculating the sample size for attribute test, reliability and confidence level is predetermined and I have to calculate sample size. Someone gave me equation

Sample size = ln(1-C) / ln (R). and this equation is for C=0 (ie. zero failure) but I don’t know where is equation came from? any idea..

and I am also looking for equation with number of failure assocaited on the equation above. I found one online calculator http://www.quality-one.com/products/inttools.php this matches with the equation above if failure is taken “0”. Please help me how this is calculated ..where do I find any textbooks …

Thanks

RameshApril 21, 2009 at 10:14 pm #159668The cumulative Binomial Distribution:

Where:

– C.L is the Confidence Level for the Test. This can be thought of as the Probability of more than the Maximum number of allowable failures occurring on Test.

– N is the number of unit on test or Sample Size

– r is the maximum allowable number of failures on test

– R is the reliability of the System for the duration of the test

With no failure, Cumulative Binomial Distribution equation is given below:

1 C.L = R^N

Solve for N

N = LN(1 C.L)/LN(R)

You can also solve top first equation for 1 failure and so own.

If you have any other question, please let me know.

Muhammad Anwar

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