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SMALL SAMPLE ACCEPTANCE SAMPLING TABLES USING MEAN LIFE CRITERIA BASED ON THE WEIBULL DISTRIBUTION (INCLUDING THE EXPONENTIAL CASE),
Research and development rept.,
NAVAL SHIP RESEARCH AND DEVELOPMENT LAB ANNAPOLIS MD
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Acceptance criteria are established for mean life requirements, assuming that a Weibull failure time distribution, with shape parameter 0.6 or beta or 3.6, applies. This includes the exponential failure distribution as a special case beta 1, and when beta 3.4, a close approximation to the normal distribution. Mean life is defined as the average time to failure of similar items operated under similar conditions. Acceptance sampling plans based on the binomial probability distribution have been developed for the mean life criterion, using sample sizes of 2 or n or 50, and acceptance numbers of zero or C or n-1, c or 8, to assure, with minimum confidence of 90 andor 95, the acceptance of lots for which the estimated mean life is equal to or greater than some specified operating time. In addition to their use as acceptance sampling criteria, mean life estimates would also be appropriate for establishing correction factors to compare basic environmental test results, with those obtained under other than basic conditions. Author
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