Not one of you respondents have mentioned the fact that if you perform the 80/80 rule on more than 2 units, you will discover that in order to pass the 80/80 test you must have a certain margin below 0 dB! (assuming that the readings from both units are not identical, an unlikely event. That margin delta erodes when the sample size increases. That is because the arithmetic mean is added to a confidence factor which includes a standard deviation and a sample size factor. When added, the sum of those must be below or equal to the limit. So, for production sampling, 0 dB margin will work out to be a failure using the 80/80 rule! Your best hope then is that when using a small statistical lot size, the arithmetic mean is small so that the added margin is small.
Hans T. Mellberg EMC Consultant. P.S. Now that the dB thing has been the popular subject of late, could someone respond to my questions about cable modem telco approval for Japan, Australia, Finland, France and UK?
