ISSN: 1945-7553
CODEN: JTEVAB
Page Count: 5

Probability, Confidence, and Sample Size in Fatigue Testing

Parida, N
National Metallurgical Laboratory, Jamshedpur,

Das, SK
National Metallurgical Laboratory, Jamshedpur,

Gope, PC
National Metallurgical Laboratory, Jamshedpur,

Mohanty, ON
National Metallurgical Laboratory, Jamshedpur,

(Received 3 August 1989; accepted 30 March 1990)

Abstract

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.

Keywords:
fatigue life, probability, confidence level, sample size, log-normal distribution, coefficient of variation, rate of change of error

Paper ID: JTE12505J
DOI: 10.1520/JTE12505J
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