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Dealing with Data 2 – It’s a scale thing

May 14, 2010

An important aspect of a graph that is often overlooked is the choice of the correct scale. I am astonished to the extent which scales on graphs are tinkered with (sometimes in a devious manner) to drive home certain arguments that are not really backed up by the data.

My personal favourite is the “Let’s start the scale at something other than zero” move, now this might be suitable at select times, but it should be made abundantly obvious to the potential reader when this is the case, particularly if you have been using a different scale in previous slides/pages etc, or your graph will only be up on the screen briefly.

Check out the example below. Let’s say I wanted to create the impression that sales in my company have SKY ROCKETED in June and July due to some brilliant initiative I have just launched, to prove this point I trot out graph A. What a shrewd business man I am, look at all that growth!

However I would have to hope that graph B never saw the light of day as it would expose me as somewhat of a fraudster… Here it is, same data, much less impressive first impression:

For me, the best policy is to start the scale from 0. But if you feel like making yourself look more impressive… just alter the scale…

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