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Sampling plan for a customer who wants AQL 1.0 (per ANSI Z1.4)

Nicole Desouza

Starting to get Involved
#1
Hi,
I need to come up with a sampling plan for a customer who wants AQL 1.0 (per ANSI Z1.4). Firstly, I do not understand what this means. Could someone please explain it? I tried looking at the tables but it's kind of confusing. Secondly, where can I find more information on sampling plans? We do a variety of different types of products for different industries. for example we are in Lighting, Medical Device and Aerospace plastics extrusion industries. I would love to know what the industry standards are for these industries so that we can set the appropriate sampling plan according to the industry.

thanks,
Nicole
 
Last edited:

David-D

Involved In Discussions
#2
Do you have a copy of Z1.4?

As a quick fill-in yoy can take a look at the historic MIL-STD-105 off of which it was based. You can download a copy free from the government at:
https://quicksearch.dla.mil/qaDocDetails.aspx?ident_number=35496

You need to know what inspection level you are usinh. Most commonly, General II is used for non-destructive samples but you might have alternate requirements.

Here's the most basic mechanism: Based on the inspection level and the lot size, use Table I to determine the code letter which equates to a sample size. Then using Table II with the code letter and AQL you can fond the sample size and the accept/reject criteria.

It gets potentially more complicated when you work in switching criteria (reduced/ tightened) double/multi sampling plans but the basics should atleast help you get started.

Best wishes,

David
 

Mike S.

An Early 'Cover'
Trusted
#4
The above posts are good guidance.

MIL-STD-105 and ANSI Z1.4 are complicated with tables that have tripped-up many a user.

I recommend getting buy-in from your customers as to what sampling plans are customary, do they require you to follow switching rules (which really complicates things), etc.

Also, many aerospace customers require "C=0" sampling plans where no rejects are allowed in the sample for the lot to pass, which is different than Z1.4 or MIL-STD-105 plans. See ASQ for a book by Nicholas Squeglia for more details on this. His plans are also much easier to understand and follow.
 

Nicole Desouza

Starting to get Involved
#5
Do you have a copy of Z1.4?

As a quick fill-in yoy can take a look at the historic MIL-STD-105 off of which it was based. You can download a copy free from the government at:
https://quicksearch.dla.mil/qaDocDetails.aspx?ident_number=35496

You need to know what inspection level you are usinh. Most commonly, General II is used for non-destructive samples but you might have alternate requirements.

Here's the most basic mechanism: Based on the inspection level and the lot size, use Table I to determine the code letter which equates to a sample size. Then using Table II with the code letter and AQL you can fond the sample size and the accept/reject criteria.

It gets potentially more complicated when you work in switching criteria (reduced/ tightened) double/multi sampling plans but the basics should atleast help you get started.

Best wishes,

David
Thanks for your help. This actually simplifies things for me :)
 

Nicole Desouza

Starting to get Involved
#6
The above posts are good guidance.

MIL-STD-105 and ANSI Z1.4 are complicated with tables that have tripped-up many a user.

I recommend getting buy-in from your customers as to what sampling plans are customary, do they require you to follow switching rules (which really complicates things), etc.

Also, many aerospace customers require "C=0" sampling plans where no rejects are allowed in the sample for the lot to pass, which is different than Z1.4 or MIL-STD-105 plans. See ASQ for a book by Nicholas Squeglia for more details on this. His plans are also much easier to understand and follow.
Thanks for your recommendations :)
 
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