posted 09 June 2000 04:10 AM              

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I am looking for an historical description of the requirements of automotive principals concerning the PPM since the giving up of the AQL. Web sites, books, reviews, ... ASAP. Thank you very much.

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From:West Chester, OH, USA
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posted 13 June 2000 01:02 AM               

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I don't know any specific sites, etc., but In my memory AQL started receeding in the late 1980's as the philosophy went from inspection to 'manufacturing responsibility'. I believe the personal computer has in part allowed this as the data necessary before could be overwhelming. In addition, the Cost of Quality started becoming 'interesting' especially as companies started trying to quantify the cost of Bad quality and had some degree of succeess. I first heard ppm in the electronics world. It might have been with respect to 6 sigma. The conversations I remember included simple stuff but most was based on the idea that there is no 'Acceptable Quality Level' (acceptable number of defects) and that serious continuous improvement was necessary. As I remember 6 ppm was a goal at many places. Damn, I've got the 'old timers' disease - can't rmember much any more.

Anyone know the equivalences between AQL and ppm? (Like an AQL of 95% is X ppm.)

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From:Britton, SD, USA
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posted 13 June 2000 03:48 PM               

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I don't know of a way to directly link AQL to PPM. To me that is apples and oranges.

Will this help?

+/- 1sigma = 68.27% = 317,300 ppm outside
+/- 2sigma = 95.45% = 45,500 ppm
+/- 3sigma = 99.73% = 2,700 ppm
+/- 4sigma = 99.9937% = 63 ppm
+/- 5sigma = 99.999943% = 0.57 ppm
+/- 6sigma = 99.9999998% = 0.002 ppm

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posted 14 June 2000 01:20 AM               

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Yup - That's what I had in mind.

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