Understanding Quantitative Accelerated Life Data Analysis

In typical life data analysis one determines, through the use of statistical distributions, a life distribution that describes the times-to-failure of a product. Statistically speaking, one wishes to determine the use level probability density function, or pdf, of the times-to-failure. Appendix A of this reference presents these statistical concepts and provides a basic statistical background as it applies to life data analysis.

Once this pdf has been obtained, all other desired reliability results can be easily determined including but not limited to:

Percentage failing under warranty.
Risk assessment.
Design comparison.
Wear-out period (product performance degradation).

In typical life data analysis, this use level probability density function, or pdf, of the times-to-failure can be easily determined using regular times-to-failure/suspension data and an underlying distribution such as the Weibull, exponential or lognormal distribution. These lifetime distributions are presented in greater detail in the Life Distributions chapter of this reference.

In accelerated life data analysis, however, we face the challenge of determining the use level pdf from accelerated life test data rather than from times-to-failure data obtained under use conditions. To accomplish this, we must develop a method that allows us to extrapolate from data collected at accelerated conditions to arrive at an estimation of use level characteristics.

This chapter includes the following subchapters: