Understanding Graphs

Data is very often displayed in graphs in the media – but graphs can be created to tell the story they media outlet wants to tell – and so obscure the truth.

Graphs show the relationship between different items of data.  Sometimes graphs can be confusing if they contain different items of data.

Confusing / Misleading Graphs

This graph from the Mail Online has a number of factors that could be misleading.

  • Shock tactics – a literacy point – the use of “shock fall” tells the reader what they want you to interpret from this graph before you even see it – but is it true?
  • The key – this graph shows two items of data.  The % quarterly growth in the bar chart with the y-axis on the left and the £ size of the economy in the line graph with the y-axis on the right.
  • Axis issues – the x-axis on this graph is confusing and appears to have missing data.  The data is actually all there but the axis doesn’t help.
mailGraph

Graph from Mail Online

This graph does not have a y-axis so the scale is misleading.  It appears as though the employment has gone up by about 300%!employment

The y-axis in this graph does not start at zero so the fall is not as dramatic as it appearsFTSEGraph

It’s quite common in the media to present bar graphs as pictograms. However the number of medals here does not really mean anything. The USA has almost 4 times as many medals as Germany yet only 3 times as many medal pictures.
medals

This bar chart is a read-out of run distances using Nike+. The X-axis is misleading as the intervals are not regular.nike+

PresidentialElections

This horizontal bar chart shows the number of supporters on Facebook for the candidates in the 2008 US presidential election. This initially appears misleading as there is no X-axis or scale. However the bars are proportional and the numbers are included. The same data (from the top graph) generated in Excel looks very similar.PresidentialElectionsExcel

This is a graph, produced by the Times to show how many more readers they have than the Daily Telegraph.  Again the Y-axis does not start at zero so it appears the Times has twice as many sales as the Telegraph. In fact it has 9% higher sales.TimesVTelegraph

A good analysis of another confusing / misleading graph on climate change can be found on the Real Climate Change website.

Watts_world_climate_widget1

 

Finally Vox.com has this excellent video demonstrating that the y-axis shouldn’t always start at zero.

Leave a Reply

Your email address will not be published. Required fields are marked *