class reliability.Reliability_testing.sample_size_no_failures(reliability, CI=0.95, lifetimes=1, weibull_shape=1, print_results=True)

This is used to determine the sample size required for a test in which no failures are expected, and the desired outcome is the lower bound on the reliability based on the sample size and desired confidence interval.

  • reliability (float) – The lower bound on product reliability. Must be between 0 and 1.

  • CI (float, optional) – The confidence interval of the result. Must be between 0.5 and 1 since a confidence less than 50% is not meaningful. Default = 0.95 for 95% CI.

  • lifetimes (int, float, optional) – If testing the product for multiple lifetimes then more failures are expected so a smaller sample size will be required to demonstrate the desired reliability (assuming no failures). Conversely, if testing for less than one full lifetime then a larger sample size will be required. Default = 1. Must be greater than 0. No more than 5 is recommended due to test feasibility.

  • weibull_shape (int, float, optional) – If the weibull shape (beta) of the failure mode is known, specify it here. Otherwise leave the default of 1 for the exponential distribution.

  • print_results (bool, optional) – If True the results will be printed to the console. Default = True.


n (int) – The number of items required in the test. This will always be an integer (rounded up).