The 80/80 rule for compliance has some more implications then one might think. If the mean emission level of your products is f.a. at 100 Mhz on 29 dbuV/m and the standard deviation in your products is 5 dB, then this implicates that more then 20% of the production is exceeding the 30 dBuV/m limit. This may happen easily if the standard deviation is calculated from a few samples. If a series of 6 contains of the following values: 29,28,29,28,22,29 , then the 80/80 rule would FAIL ! Using the following series: 29,28,29,28,27,29 , the 80/80 rule would PASS
As you may easily see, a full compliant series close to the limit may fail the 80/80 rule if extrapolated to a full production run. I have available for those interested a spread sheet for calculations of the 80 80 rule, i once downloaded from a site, upon instigation of one of this list's members. I do not remember who, how and where, but the author deserves the credit , not me ! May he (she) rise ! Regards, Gert Gremmen, (Ing) ce-test, qualified testing =============================================== Web presence http://www.cetest.nl CE-shop http://www.cetest.nl/ce_shop.htm /-/ Compliance testing is our core business /-/ =============================================== >>-----Original Message----- >>From: owner-emc-p...@majordomo.ieee.org >>[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of >>geor...@lexmark.com >>Sent: Tuesday, November 20, 2001 2:53 PM >>To: Gregg Kervill >>Cc: emc-p...@ieee.org >>Subject: RE: 80/80 rule for euro compliance? >> >> >> >> >> >>Actually, Vilfredo Pareto (1848-1923) was an Italian economist. >>He observed that 80% of the economy was driven by 20% of the >>consumers, i.e. 20% of the customers account for 80% of the >>turnover. >> >>Two decades ago I was involved in an effort to create a data bank >>of IBM typewriter service customers. Some customers (e.g. banks) >>owned many units, and placed many calls for service, while fewer >>calls came from individuals owning one machine. It became evident >>that 20% of the customers accounted for 80% of the service calls. >>The data base was set up to maintain the phone numbers of only the >>most active 20%, as this required 80% less computer space. When a >>call came in, the customer was asked for their phone number. If it >>was one of the 20%, the operator then saw a full screen of data as >>to the name, address and service history of the customer, saving >>time on the phone keying data. >> >>It would probably be correct to say that 80% of the work is done >>by 20% of the workers; however, it would still take 100% of effort >>to complete 100% of the work. >> >>George Alspaugh >> >> >> >> >>"Gregg Kervill" <gkervill%eu-link....@interlock.lexmark.com> on 11/14/2001 >>08:03:00 AM >> >>Please respond to "Gregg Kervill" >><gkervill%eu-link....@interlock.lexmark.com> >> >>To: "'Doug McKean'" <dmckean%corp.auspex....@interlock.lexmark.com>, >> "'EMC-PSTC Discussion Group'" >> <emc-pstc%majordomo.ieee....@interlock.lexmark.com> >>cc: (bcc: George Alspaugh/Lex/Lexmark) >>Subject: RE: 80/80 rule for euro compliance? >> >> >> >> >>Liars, Damn Liars and ..... >> >> >> >>I sounds like the Pareto's law from management statistics "You >>can do 80% of >>the work with 20% of the effort..." >> >> >> >>I think someone requoted it once as "You an fool some of the people all of >>the time....." >> >> >> >>Cynically yours Gregg >> >> >> >> >> >>------------------------------------------- >>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: >> majord...@ieee.org >>with the single line: >> unsubscribe emc-pstc >> >>For help, send mail to the list administrators: >> Michael Garretson: pstc_ad...@garretson.org >> Dave Heald davehe...@mediaone.net >> >>For policy questions, send mail to: >> Richard Nute: ri...@ieee.org >> Jim Bacher: j.bac...@ieee.org >> >>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. >> >> >> >> >> >> >> >>------------------------------------------- >>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: >> majord...@ieee.org >>with the single line: >> unsubscribe emc-pstc >> >>For help, send mail to the list administrators: >> Michael Garretson: pstc_ad...@garretson.org >> Dave Heald davehe...@mediaone.net >> >>For policy questions, send mail to: >> Richard Nute: ri...@ieee.org >> Jim Bacher: j.bac...@ieee.org >> >>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. >> >>
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