Without going into the mathematics, you can demonstrate that your product meets an 80 / 80 requirement with eight units all of which meet the requirement.
The mathematics is based upon the Binomial Distribution. The first 80 is the probability of success. The second 80 is the confidence that all units will meet the requirements with an 80 % probability of success. The mathematics makes no assumption on the distribution, for example, whether the test data has a normal (Gaussian) distribution. The Binomial Distribution, b(x;,n,p), is used to calculate the expected number of success in x out of n trials for a given p Probability of Success b(x;n,p) = ( (n!)*(p^n)*((1-p)^(n-x))/((x!) * ((n-x)!)) The Cummulative Binomial Distribution, B((x-1);n,p), is used to calculate the confidence demonstrated by x successes ofut of n trials for a give p Probabilityof Scccess. Here is a short table of results 1 unit tested, 1 unit passed, 50 % probability of success, 50 % confidence 2 units tested, 2 units passed, 60 % probabilityof success, 60 % confidence 3 units tested, 3 units passed, 65 % probability of success, 65 % confidence 4 units tested, 4 units passed, 70 % probability of success, 70 % confidence 5 units tested, 5 units passed, 75 % probability of success, 75 % confidence 8 units tested, 8 units passed, 80 % probability of success, 80 % confidence 14 units tested, 13 units passed, 80 % probability of success, 80 % confidence 21 units tested, 19 units passed, 80 % probability of success, 80 % confidence Best regards Bob Schlentz ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
