AQL for Laymen - ANSI/ASQ Z1.4 - MIL-STD-105

[The Fixer]

I know you people have headier topics to discuss but I need to make a plain english statement in a document concerning AQL and need a little help. Please evaluate this statement based on MIL-STD-105.

"An AQL of 1.0 means that a lot that is 1% defective will pass 95% of the time."

Thanks,
Glenn

[Dave Strouse]

Glenn -

The meaning you write may be true for some specific plan. However, not all plans will accept at 95% of the time.

Don't have my copy of MIL-STD-105 handy, but it has been supplanted by ANSI/ASQ Z1.4 anyway and it says the same as references below, I believe.

Reference ANSI/ISO/ASQC A3534-2-1993 Statistics- Vocabulary and Symbols - Statistical Quality Control , ANSI/ASQC Z1.4-1993 Sampling Procedures and Tables for Inspection by Attributes and, ANSI/ASQC S2-1995 Introduction to Attribute Sampling.

AQL is generally defined as "That level of quality acceptable to the consumer as a long term process average". In day to day terms, it means that the great majority of lots with quality equal or better than AQL will be accepted by the sampling scheme employed. They do not quantify the % acceptance of lots. For that you need to look at the OC curve of the specific plan selected.

Hope that helps.

[Marc]

Does anyone have a good scan of the tables?
MIL-STD-105E

[The Fixer]

I have both the MIL-STD and the ANSI/ASQ Z1.4. After reviewing Dave's comment and re-examining the OC curves, I can see that for a given AQL the Pa for a series of lots varies with the sample size as well as the %defective (process average). So that, Code letter E for sample sizes 26-50 @AQL=1.0 says that if the pct def average is .077, the plan will accept 99% of the time but if the pct def average is .394, the plan will only accept 95% of the time. So, my "laymen's" statement turns out to be "The AQL is an index that determines the quantity of defects that are likely to be accepted by the sampling plan." So, less risk mean a lower AQL number and a lot more $$ to implement it. The business decision is a trade off.

[cochranemurray]

This is a useful site if you cant be bothered with the tables.
Military Standard 105E (ANSI/ASQC Z1.4, ISO 2859) Tables

[Marc]

Good link, cochranemurray! Thanks!

[Engr.gauravnarula]

But i need details !!

[harry]

Could you mention what are the details you need - otherwise no body can help you.

Before you do that, do us a favour. Go to the bar at the top of the page (blue in colour) and look for the 'search' function. Key in '105', set it to search for the whole forum and you'll be directed to the search engine. Key in 'mil std 105', 'search the forum' and you'll get about 2-3 pages of past discussions. I believe what you needed should be there!

Welcome and enjoy yourself.