I’ve recently been reading Edward Tufte’s Visual Display of Quantitative Information. It introduces several interesting metrics for the analysis of data graphics such as the data-ink ratio and my personal favourite, the lie factor.
The lie factor is defined as the size of the effect shown in a graphic divided by the effect shown in the data. A great example of this comes from FlyZoom’s website, which describes the difference between standard and premium seating. Seats in standard class are set at a 31″ pitch while those in premium are at 36″ pitch. However this is the graphic they use to illustrate it:
Measuring the figure, the 31″ pitched seats just happen to be 31 pixels apart (i.e. back of one seat to the back of the next). However the 36″ seats are 43 pixels apart. That means a lie factor of (43-31)/(36-31) = 2.4.
Doesn’t look quite so comfortable now, does it?
