Distribution of a Life Ratio and Its Application

This paper consists of two parts, both of which are concerned with a ratio of two lives from life test data. Part 1 derives an exact distribution of the quotient of two random variables, each of which follows the truncated extreme-value distribution. Then graph of the cumulative distribution function is given for several values of a parameter. Part 2 develops a control chart for sample ratios to be used in controlling the deterioration of quality characteristics having an extreme-value distribution.