Wednesday, 10 June 2015

Are you answering the right question?

I bring before you the story of statistician, Abraham Wald.

During World War II, Wald was part of a team looking at the problem of bomber loss and to consider how they should reinforce the planes to better protect them. The problem was proposed that they should look at the frequency of damage sustained by returning bombers and to use that information to make recommendations on where the plane should be reinforced.

Wald's brilliant insight was to turn the problem on its head. He suggested that the places where the returning planes were being damaged most frequently were the places where those planes could actually sustain damage and, mostly, successfully return to base. What the question should really be is where the planes that weren't returning were being damaged which meant that they failed to return!

It seems so simple when you think about it, but sometimes we are so sure that we are looking at the problem the right way, that new insight that tells us that we are looking at it completely wrong is not always well received. But we should receive it and we should look at it and only dismiss it if we can logically decide that it should be dismissed.

So, think outside the box and solve this problem:

Here is a pattern of 9 dots, arranged in a 3x3 grid:

Now, I want you to connect the pattern of 9 dots using four straight lines drawn without lifting the pen from the paper or retracing any lines. Simple, eh?

Please don't post solutions below. If you discover it, just be happy that you have done so and feel good that you have thought differently and bring that skill to your daily work.

Stephen Redmond is a Data Visualization professional. He is author of Mastering QlikView, QlikView Server and Publisher and the QlikView for Developer's Cookbook
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  1. Great post Stephen. The brain teaser even better :)

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  3. Hi, Stephen. It is good to say that it is possible draw lines out of dots to any distance. Because on image you have a visual border. It is very important and not clear for all :-) Not all people see here is no other limitations but don't lift a pen.