# sample_size_no_failures¶

class reliability.Reliability_testing.sample_size_no_failures

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.

inputs: reliability - lower bound on product reliability (between 0 and 1) CI - confidence interval of result (between 0.5 and 1). Defaults to 0.95 for 95% CI. lifetimes - 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 is 1.
weibull_shape - 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 - if True the results will be printed to the console.

returns: number of items required in the test. This will always be an integer (rounded up).