The Red Bead Game Applied to Medical Errors


A blog reader sent me a link to this UK news article — really, it's a lesson in statistical literacy, so thanks to the BBC for that. In the web piece, “Can chance make you a killer?“, Dr. Deming's famous lessons from the “Red Bead Game” are illustrated in the context of deciding, based on data, which hospitals or doctors have patient death rates so high that negligence would be implied.

Are you fluent in the terminology and concepts of “common cause” and “special cause” variation? The BBC provides a great primer.

I have facilitated the Red Bead Game a number of times, after having read about it Dr. W. Edwards Deming's classic Out of the Crisis. I own a copy of the kit, as pictured above, which I used at a healthcare conference a few years back.

Some of the lessons learned from running this game:

  • Arbitrary quality targets are useless if the system is not capable of delivering that level of quality
  • People are often punished or rewarded for situations that are just “dumb luck” instead of anything reflecting their skill or ability

The BBC article lays out an example and an interactive simulator to help you walk through this situation:

We've devised a chance calculator to simulate this scenario. It is set up so that you are innocent of any failing. But bad luck might convict you all the same.

In the real world all kinds of factors make a difference, like surgical skill. But in the calculator, every patient in every hospital has exactly the same chance of dying and every surgeon is equally good. This is to show what chance alone can do, even when the odds are the same all round.

  • The calculator (below) shows 100 hospitals each performing 100 operations
  • The probability that a patient dies is initially fixed at five in 100
  • The government, meanwhile, says death rates 60% worse than the norm are unacceptable (in red)
  • So any hospital which has eight deaths or more out of 100 ops – when the expected average is only five – is in trouble.
  • We've assigned one hospital to you, with a box around it – it could come out green or red.

This is just brilliant. Instead of reading what I'd have to say, go to the BBC site and play around with the simulator. Hit “recalculate” many times. How often is “your” hospital deemed “good” or “bad” due to just random chance?

Come back here and comment, though, please if you have thoughts to share.

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  1. John Hunter says

    For those interested in more details on the red bead experiment I have some additions resources on my Curious Cat site.

  2. Mike Johnson says

    John the Red Bead Discussion Group on LinkedIn

    over 180 experts from all over the world


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