• http://www.qualityinspection.org/ Renaud Anjoran

    Good question!
    As you have probably guessed, the numbers are lower for the producer, since the buyer’s risk is higher than than the producer’s risk.
    You can see them in the below image.

  • Philipp Toth

    Dear Renaud,

    thanks so much for running this blog – it is a very, very helpful read! I have one question in regard to defining the correct LOT (# of
    homogeneous units) within the IQC environment:

    According to my understanding, a LOT should be quantified by
    “A defined quantity of starting material, packaging material or product
    processed in one process or series of processes so that it could be expected to
    be homogeneous”. The number of items in such a production lot forms the
    correct base to size an AQL inspection sample.

    Controversially, I see the practice that Chinese
    manufacturers define the LOT size based on individual micro order quantities,
    which are not linked at all to the above manufactured batch homogeneity, in
    particular when the order sizes are small and only define the pull quantity for
    a vendor managed inventory (VMI), the later stocked by an a.) independent and
    b.) very different tact & batch definition.

    Applying on such VMI pull lot size the AQL based sample
    seizing approach must be wrong for the following reason:

    • The VMI pull lot does not reflect necessarily the unconformity patterns of the
    production batch, thus making any statistical derivations or statistical
    statements in regard to sample robustness useless.

    If above is correct, it would imply, that the right lot size
    for AQL sampling should be either the production batch (optimal) or something
    which is mirroring this production batch, such as a container shipment
    reflecting somehow a sub-sum of homogenous production batch. Wrong would be a pull quantity, which is not
    linked to the production process of one homogeneous batch of supplies, but more
    to a stocking methodology, which can be rather unspecified.

    I would be very interested in your statement to the
    above! Thanks a lot, Philipp

  • http://www.qualityinspection.org/ Renaud Anjoran

    Philipp,
    According to the ISO 2859-1 standard, clause 3.1.13, a “lot” is a “definite amount of some product, material or service, collected together”. And they add this precision: “NOTE An inspection lot may consist of several batches or parts of batches.”
    So I think you are a bit too restrictive in your approach.
    But your general reasoning does make sense.

  • Alex Z.

    Let’s say we have Critical, Major and Minor defects. Within Minor defects list we have flash, burn mark, sink mark, bubble, etc. If we set different AQLs for each of these defects (flash – 0.25; burn mark – 0.4; sink mark – 1.0, etc.) how do we establish if the lot is accepable or not? Do we need to meet AQL requirements per defect? or do we need to count all Minor defects together and make sure that the number meets lowest AQL from the entire list of Minor defects?
    Thank you!

  • http://www.qualityinspection.org/ Renaud Anjoran

    You should set limits for each category (Critical, Major and Minor defects). Then decide what defects go in what category. And finally you add up the defects you have found in each category.

  • anwar quadri

    can we do inspection for major and minor on same level as 2.5 % i.e. 10 defect each

  • http://www.qualityinspection.org/ Renaud Anjoran

    Sure.

  • Loader2000

    AQL IS NOT the “quality level that is the worst tolerable”. It is the ‘best case failure rate’, assuming you barely pass your inspection. Based on the table, for an AQL of 2.5%, the plan would allow 5% (10 out of 200) failures for inspection level II. Clearly, 2.5% is not the worst case when the plan allows 10 out of 200 to fail. The lower confidence limit of the failure rate (in the worst case) is the AQL. In the case of the two circled columns in the second table, the lower confidence limit of the allowable failure rates given are 2.5% (for 10 out of 200) and approximately 4% (for 14 out of 200). The conventional definition of AQL is completely misleading and totally bunk. I almost think it was deliberately designed to favor the producer (and mislead the customer) so that the originators of the tables could actually sell them to companies. Companies would then think, “Hey I can achieve and AQL of 2.5% with a failure rate of 5%. That great, lets buy those tables.” In reality, RQL is worst case, assuming you barely pass your inspection. RQL is the 95% upper limit of the failure rate (using exact CI) given that you just barely pass your inspection criteria. In any industry where the customer could be harmed by bad product, RQL is the only measure that should be used most of the time.

  • http://www.qualityinspection.org/ Renaud Anjoran

    No, you are mistaken. There is a reason why an AQL of 2.5% actually results in accepting up to 10%.
    If you want to learn more about this topic, watch the 3 videos I posted on Youtube (link at the end of the above article).

  • anwar quadri

    my field is bed linen production in huge bulk quantity . can u give tips on self quality management system to control required quality during production i.e cutting , stitching, checking , packing and shipment

  • http://www.qualityinspection.org/ Renaud Anjoran

    Wow, that’s a pretty wide subject. A rough overview is on http://www.qualityinspection.org/increase-quality-china/ — but not all elements are applicable for producing linen.

    Where is your factory based?

  • Loader2000

    Regarding my previous question (or comment) you can email me at statbio.cg@gmail.com if you have an answer. I still think using RQL (or LTPD) is the best way to go. I’m sure you address that on one of your other pages. You can remove this comment.

  • http://www.qualityinspection.org/ Renaud Anjoran

    I suggest you watch the 3 videos I posted on Youtube (link at the end of the above article). It should clarify the subject.

  • ayubu mbuka

    is any site i can visit and learn more about AQL?

  • subrta pal

    Thanks

  • Selva Rajan

    Hello, would like to know when we perform sampling checking, should the samples acquired be in 1 bag or few bags? Eg. Lot size is 1200 pcs which comes in 4 bags. Should I take the 32 pcs from the same 1 bag or from the 4 bags to make up 32 pcs? Pls advice. Tq.

  • http://www.qualityinspection.org/ Renaud Anjoran

    The ISO 2859 standard says nothing about this, but there are general conventions in the inspection industry. Take the samples from at least 2 bags (square root of 4).

  • Selva Rajan

    Tq Mr Renaud.

  • Someone

    hello, let’s say that my supplier had a failure and i had to reject a lot of his items. after we looked for a solution it was decided that he will perform a 100% visual inspection on the items and only then will send them to me. now, i want to see that the corrective action was effective and want to perform an extensive visual inspection once i receive the product. what would you recommend? if the lot size is 500,000 will it be enough to inspect 25,000 pieces?

  • http://www.qualityinspection.org/ Renaud Anjoran

    I’d advise to follow the standard I introduced in this article. I’d say you want to follow level II or level III (certainly not level I). And, if that supplier has already failed at least twice over the past 5 shipments, you want to follow a tightened severity rather a normal severity.

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