Use of the Weibull versus Exponential to Model Part Reliability

The best practice for characterization of the reliability parameters for a part from historical or empirical data often erroneously uses the mean-time-between-failure for the exponential probability distribution. The use of the exponential probability distribution for parts that experience wear during its useful life overstates the reliability and availability of a part early in the useful life and then understates the reliability and availability later. This error contributes to logistical support confusion for the life cycle costs for spare parts and maintenance. The use of the Weibull distribution is more accurate and practical. It is shown that the Weibull best models the reliability, maintainability and availability of parts that have a variable hazard rate over its useful life