AQL VALUES IN SAMPLING SCHEMES

[Former Member]

Hi QM Team,

We use AQL Value in Sampling schemes. AQL Value is nothing but Acceptable quality level. Along with this AQL value we also define sampling plan in sampling schemes. In sampling schemes we have to define C1 & D1 values.

Now C1 is nothing but :For an attributive inspection, the highest number of nonconforming units or the highest number of defects in a sample that leads to an acceptance of the inspection lot.

and D1 is nothing but : For an attributive inspection, the lowest number of nonconforming units and/or the lowest number of defects in a sample that results in a rejection.

So by defining C1 & D1 we are defining acceptable quality level .

So my question is WHY AQL VALUE IS REQUIRED ? OR IN THE OTHER WAY HOW AQL VALUE WORKS WHEN WE HAVE ALREADY DEFINED C1 & D1? WHICH TAKES PRECEDENCE C1&D1 OR AQL VALUE

[Former Member]

If while creating sampling scheme, if more than 1 AQL values are set (say 1.5,2.5 etc); at the time of assigning this sampling scheme in sampling procedure, we can select the AQL level.So level selected will be applicable for that sampling procedure.

Vishal

[Former Member]

Hi Vishal,

can u please explain use of AQL Value . I am totally confused with this AQL value and inspection severity.

[Former Member]

First understand Inspection severity.Forget about AQL.See, there are different inspection severities ex. normal, tightened,reduced.

So for same lot size, sample size will be different for different severities.

For ex. for lot size 100, sample size is 7 for normal severity.But for tighted it will be more than 7, say 10 and for reduced it will be less than 7, say 5.

So inspection severity will decide the sample size in such a way.

Now what is AQL?For same inspection severity, there may be different AQL.

Say in case of normal inspection severity, sample size is 7.

AQL is acceptance quality level.if say AQL is 1.5

So for AQL 1.5 acceptance no. is 2.Means if 2 samples are rejected max, lot will be accepted.

If say AQL is 4.0, acceptance no. will be more than 2, say 3.Means if 3 samples are rejected max, lot will be accepted.

So AQL will decide, acceptance or rejection of lot.

I hope I have explained in detail.

Vishal