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Design of Experiments Guide > Accelerated Life Test Designs > Statistical Details for the ALT Design Platform > R Precision Factor (for a 95% CI)
Publication date: 11/29/2021

R Precision Factor (for a 95% CI)

The R precision factor is a measure of the precision of the estimate of tp, the pth quantile of the failure time distribution. An approximate 95% confidence interval for log(tp) is:

Equation shown here

resulting in a confidence interval for tp;

Equation shown here

where

Equation shown here

To obtain R, use the large sample approximation of the variance of the log(tp):

Equation shown here

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