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Life-test data on subminiature vacuum tubes designed for 5,000 hours are analyzed statistically and an equation is derived for the curve of life survival percentages. Correlation of individual types to the general curve is found to be extremely high. Controls are determined for normal 500-hour life tests which assure rated long-life quality and are presented as a method for evaluating life expectancy before completion of long-life tests. Life test samples of lots of tubes released by this 500-hour plan were continued in operation for 5,000 hours, and the results are shown to be satisfacfactory.