Quality Control Doesn’t Work (and how to fix it)


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Here is a bold statement, inspection doesn’t work; (literally bold). Yet every organisation I have ever worked for uses and pays for quality controllers. They can’t all be wrong can they? What makes me think I am so right?

Maybe, if you read this I will convince you: The shadow illusion, or perhaps this: Fooling yourself.

Have I persuaded you?

It is always better to get rid of your problems at source than rely on somebody to weed them out later.

But sometimes you need to have quality control

Sometimes you have no choice. You need to rely on inspectors. Can you imagine getting onto an aeroplane without somebody looking at your bags first? How comfortable would you, as a paying customer, feel about that? Particularly if the gentleman behind you looked a little dodgy.

So how can you make inspection work?

One of the problems with quality inspection is the “vigilance decrement”, the accuracy or speed of detection diminishes over time.

Put another way inspector’s minds wander, they start to daydream.

The less likely they are to find an item, maybe a bomb in a bag, the more likely they are to be thinking about their next holiday.

Can you imagine looking at an x-ray screen day in day out? (Or for that matter listening to calls, or checking hotel rooms are clean?) I would be bored out of my tiny mind. Wouldn’t you?

So how do you spice things up?

How do you make an inspectors job more challenging and interesting?

  • Give them feedback. Instead of just measuring their “hit rate” also measure their “false positive rate”. How often did they think there was something there when there wasn’t? (Measures are one thing targets are something totally different)
  • Add false signals. If only one in a billion bags has a real bomb it is hardly surprising if it gets missed. If, however, one in a thousand does, even if it is a fake one, then chances are your inspectors will be a whole lot more alert.

Mind you, if you can, it is still better to error-proof your system in the first place. It would be a little more than embarrassing if your planted bomb got through.

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