Volume 18, Issue 6 (November 1990)
Probability, Confidence, and Sample Size in Fatigue Testing
The sample size necessary for a statistically significant life test has been determined, and a comparison of actual and predicted lives has been made for a desired probability of survival with a given confidence level, statistical error, and coefficient of variation at different stress levels. This approach has been used for cases where data follow a log-normal distribution. On the basis of this approximation, it is possible to estimate the lower tolerance limit using a minimum number of samples. It has also been concluded that, whatever the sample size, the estimate always results in some error, R0, which mainly depends on confidence level, probability of survival, and stress level, and that, beyond a specified sample size, fatigue life estimation is independent of sample size.