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 …
The cumulative Binomial Distribution:
- 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.
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