Sampling - Clause 8.2.4 - What do the words "known non conformities" mean here?

S

Sohail

#1
1. Refer to clause 8.2.4 "The plan shall preclude the acceptance of lots whose samples have known non conformities"

Now this statement is very confusing to me. Does it mean that NO REJECTIONS ARE ALLOWED IN THE CHOSEN SAMPLES? i.e AQL is not acceptable in sampling inspection of AS9100 REV B QMS? That means if take statsitically valid sample of rivets (say 20 out of 1000) and if even one rivet is rejected then the lot must be rejected or the lot must be 100 percent insepected?

What actually word "known non conformities" mean here? Does it mean that the lots whose previous history shows that there are usually non conforming parts in this type of lot, or does it mean that after inspection some non conformities are found in the sample chosen.

Is sampling standard 105 E obsolete?

I hope i have explain my question well.

Thanks:confused:

2
 
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antoine.dias

Quite Involved in Discussions
#2
Re: Sampling - Clause 8.2.4

It means exactly that. No non conformities are allowed in the sampling.

It also means that the AQL can only be used to have a good basis for number of samples to be taken from a certain lot. AQL cannot be used for release criteria of the lot.

There is something similar in the ISO TS 16949 ( when sampling is used for attribute testing the acceptance criteria must be 0 defects )

Best regards,

Antoine
 

Mike S.

Happy to be Alive
Trusted Information Resource
#3
Does it mean that NO REJECTIONS ARE ALLOWED IN THE CHOSEN SAMPLES? i.e AQL is not acceptable in sampling inspection of AS9100 REV B QMS? That means if take statsitically valid sample of rivets (say 20 out of 1000) and if even one rivet is rejected then the lot must be rejected or the lot must be 100 percent insepected?


Is sampling standard 105 E obsolete?


2
Yep, the sample must have no nonconformities -- also known as a "C=0" sampling plan.

You can use an AQL chart -- like MIL-STD-105/ANSI Z1.4, etc. and set the number of allowed defects to zero as one way to get a decent C=0 sampling plan. Also check out a book by Nicholas Squeglia called "Zero Acceptance Number Sampling Plans" for another route to take.
 
B

BadgerMan

#4
That means if take statsitically valid sample of rivets (say 20 out of 1000) and if even one rivet is rejected then the lot must be rejected or the lot must be 100 percent insepected?
You have made the correct interpretation. :agree1:

Your acceptance number will be zero defects (C=0) and your reject quantity will be one defect or defective item.
 

clara

Involved In Discussions
#5
1. Refer to clause 8.2.4 "The plan shall preclude the acceptance of lots whose samples have known non conformities"


2
Dear all,
I am a new member, I am working for a company providing aircraft equiment in Asia. We are auditing against the AS9100 standard.
Concerning this requirement, I would like to know if it has to be applied to the incoming inspection acitivity ?
Thanks very much for your advices.
Clara
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#7
Dear all,
I am a new member, I am working for a company providing aircraft equiment in Asia. We are auditing against the AS9100 standard.
Concerning this requirement, I would like to know if it has to be applied to the incoming inspection acitivity ?
Thanks very much for your advices.
Clara
the short answer is yes.
however, remember that rejected lots are subject to preliminary review and disposition. you could screen the incoming lot, have your vendor screen it, rework it, or submit a request to repair it or "use as is"...
 

clara

Involved In Discussions
#8
Dear BadgerMan and Bev D,
Thanks very much for your reply .
It's clear now and I have apply the Zero Acceptance Number Sampling Plan developped by Nicolas L. Squeglia for our incoming inspection .
Very pleased to have chance to work with you.
Have a nice day.
Clara
 

clara

Involved In Discussions
#9
Yep, the sample must have no nonconformities -- also known as a "C=0" sampling plan.

You can use an AQL chart -- like MIL-STD-105/ANSI Z1.4, etc. and set the number of allowed defects to zero as one way to get a decent C=0 sampling plan. Also check out a book by Nicholas Squeglia called "Zero Acceptance Number Sampling Plans" for another route to take.
Dear everybody,
I would like to know , in incoming inspection, can we apply the exemption mode when the preceding 10 lots are accepted ?
Thanks for your advices.
Clara
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#10
Dear everybody,
I would like to know , in incoming inspection, can we apply the exemption mode when the preceding 10 lots are accepted ?
Thanks for your advices.
Clara
if the standard quoted by tthe original poster applies to your organization - or if a similar requirement is placed on you by any other standard or Customer - then the answer is NO. acceptance sampling *in general* applies to the lot in front of you. (the past cannot predict the future - the process may have changed since the last 10 lots and you must deal with what you have now.)

If you are under no written/explicit requirement to have a zero acceptance sampling plan you can do whatever you want. However, my advice woudl be to use zero acceptance sampling plans as most Customers these days are intolerant of any shipped non-conformities. and the best approach as always is to not use a single source of data for your decisions. SPC, continual improvement, Problem solving methods, etc. should be working as a system to improve your quality. Focus on improving the process and not whether or not you should accept a lot if it you find one or more defects in the sample
 
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