Six Sigma

The Critical Difference Between Defects and Defectives

By Ron Pereira Updated on May 27th, 2009

Today I submit a quick, but extremely important post if you produce a product of any kind.

There are two different ways your product can be “bad.”

It’s defective

First, said product can be defective. This is to say something is wrong with it. It doesn’t work like it’s supposed to. It doesn’t look like it’s supposed to. The customer, who pays you good money, ain’t gonna be happy with said product.

It has multiple defects

Second, the aforementioned defective product might have multiple defects. This is to say there are many things ‘wrong’ with the product. It has 103 different scratches all over it, 14 surface mount components are not soldered correctly, and the text on the label is incorrect in 3 different places.

Manage the defects

In summary, it only takes one defect to create a defective product. But a single defective product can have a zillion defects.

What does this me to you, maker of said product? You need to stop focusing on how many defective units you produce… instead you should be laser focused on the number of defects you’ve created the past month.

Do you agree? Is this how you manage your business?

  1. T.J.

    May 27, 2009 - 7:29 pm

    Never heard it put like this but makes sense.

  2. TJBraun

    May 28, 2009 - 6:15 am

    To pose an answer to the age old question, How many angels can dance on the head of a pin? A unit can have infinite defects and each defect can have its own assignable cause. Therefore, each defect is improtant when taking corrective actions to prevent reoccurence of the defect.
    Using the standard metric of defects per million opportunities or DPMO should allow the manufacturer to mitigate the defective unit mentality and capture the cumulative effects of multiple defects within a single unit.

  3. Mike

    May 28, 2009 - 6:57 am

    I disagree. I see two important metrics here. I’ve always been one to disagree that DPO or DPMO is the only quality metric one should look at. Think about a very complicated assembly with thousands of opportunities per assembly and one or two defects per part but many defectives throughout the production run. Compare that to a simple part with few opportunities and not very often a part is defective. The DPMO could be the same for both situations but paint a totally different picture looking at the actual process. A good way to cheat this metric is to increase the possible number of opportunities for a defect to decrease the DPMO (sure, a meteor might hit my part causing a defect, but this time it didn’t). Which this all begs the question, how do you classify an opportunity for a defect.

    Looking at first time throughput yield is a good metric to look at defectives/total produced. A more detailed metric beyond that (secondary metric) should be average defects/defective. I’ve always thought this combination of metrics paints the clearest picture of a process.

  4. Observer

    May 28, 2009 - 11:28 am

    Can’t agree more. Basically defects are to be eliminated. Without eliminating them defectives can not be eliminated. If 5 things on the average are wrong in one unit, practically every unit will go through a rework.

  5. Scott

    May 28, 2009 - 1:38 pm

    First from the customer’s perspective it is either totally correct or defective. In the customers eye’s it is also defective if it was not delivered on time, packaged correctly, and has the correct paper work for receipt and possibly certification. Producing a product to spec can only be tainted by not executing the total process. Let’s not forget the metrics for the rest of the process.

  6. Ken Walton

    May 30, 2009 - 7:04 am

    IMHO, Defects on product, can be still be accepted if within certain tolerances set by customer.
    Defective……..The product is not functioning properly, or is by no way acceptable in any way or form. No tolerances, whatsoever.

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