Validate 99.5% reliability 90% confidence - Sample size calculation
If I state a component is 99.5% reliable at 90% confidence, I can calculate the sample size needed to validate the R&C target is 460 samples. I would expect to see .5% cumulative failures in the field for the life of the product. Sample size = ln(1-C)/ln(R)
Someone has stated if the test is performed using the 95th percentile usage profile (more harsh usage profile than the median user), then I can validate the same reliability using a smaller sample size. For example, I can use a sample size of 22, to meet 99.5% reliability with 90% confidence if I use a 95th percentile usage profile. I expect .5% cumulative failures in the field for the life of the product?
Are the previous statements correct? Can I reduce the sample size from 460 to 22, and validate 99.5% reliability of the population by adjusting the usage profile?
I test to R90/C90, I need 22 samples.
Population Reliability = 1-(1-95th percentile user)(1-Reliability)