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Dealing with Data 1 – Choosing the right chart type

May 10, 2010

I recently undertook some work for a client that involved a great deal of work with data. Some of the slides in his presentation were prepared by an excel “expert” who had been brilliant at calculating the data, but in my opinion a little lacking in terms of expressing it. The slides included pie charts which contained, and I kid you not, up to 16 segments. I don’t know if you have ever seen a pie chart with 16 segments, but it is not a pretty site, and it takes quite a while to decipher exactly what is being displayed.

So the lesson learnt it that it is worth keeping in mind that the type of graph you use can greatly affect how people will understand your data. Let’s take a look at some imaginary data and see how easy it is to understand.

– Which team has greater sales Team B or Team G? –

Option A – 3d Pie chart

For some reason people like to use 3d effects when displaying their data, presumably under the impression that this will make their data a little bit more “exciting”. The fact is that data need not always be visually “exciting” – it should be clear and understandable, that is why you are showing it in the first place. It should be your actual findings that are exciting.

Look at the 3d pie, and ask yourself which section is bigger B or G? You can probably guess which one, but it is not easy.

Option B – 2d Pie chart

The same data is included below, is it any easier to find out which segment is bigger? Perhaps a little bit, but not very.

Option C – Bar chart

Again, the same data is included below, this time expressed with a bar chart. Now it is much easier to tell which is the larger segment, and to what extent.

It is even easier to compare the two at a glance when we highlight the two teams in a different colour.

… So think about how you choose to display your data, it can make a large difference in how it is understood and remembered.

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One Comment leave one →
  1. May 10, 2010 5:52 pm

    This topic has been discussed in more detail by Stephen Few here:

    http://www.perceptualedge.com/articles/visual_business_intelligence/save_the_pies_for_dessert.pdf

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