From: Stan Hilliard
Date: 30 May 2003
Time: 11:32:42
Greetings Ahmed,
>What AQL, LTPD mean ?
You can see the meaning and usage of AQL and LTPD in the sampling plan tutorial at www.samplingplans.com/modern3.htm There, the LTPD is called RQL, but they are different words for the same thing. AQL and RQL are levels of quality that correspond to the producer's point and the consumer's point of the oc curve. Be sure that you understand the oc curve because it is the most important aspect to understand how a particular sampling plan is performing for you.
> How can I choose values for AQL and LTPD ?
The tutorial that I referred to above will give some guidance, but you have a special issue to deal with related to small lots. The usual calculations of sample size assume that you have large lots -- relative to the sample size. In your example, you sample almost half of the items in the lot.
Before I can tell you more about your particular plan, please post what acceptance number you are using. Other questions that I have are: is the inspection destructive of the item?
Also, unless it is confidential, what are the items of product and what are the characteristics that are inspected?
I hope to include a calculation for small lots in my next update to my TP105 software program -- which will be available shortly. If you send me an email with your fax number and mailing address I can send you an article that describes the method and how to do it manually.
Sincerely, Stan Hilliard
shilliard@samplingplans.com