Bias in Presenting Quantitative Data

Newspapers can ‘bias’ the presentation of quantitative data by stretching out the scale of the data they present, making differences between bars seem larger than they actually are (or vice versa!).

Quantitative research methods are usually regarded as being more objective than qualitative research methods as there is less room for the subjective biases and interpretations of researchers to influence the data collection process in quantitative research.

However, bias can still creep into quantitative research and one way this can happen is over the decision in how to present the data in even a basic visualisation.

Specifically, one can take the same data and stretch out the scale of a graph displaying that data and give the impression that the differences between the subjects under investigation are wider than in the original presentation.

Bias in scaling graphs

A recent example of what I’m going to call ‘bias in scaling graphs‘ can be found in how an article by The Guardian displays recent data on how much GDP (Gross Domestic Product) has grown in different European Countries between 2019 to 2022.

the same data from the Office for National Statistics in a more ‘stretched out’ scale which

The Guardian article (September 2022) in question is this one: UK is only G7 country with smaller economy than before Covid-19 which displays the following graphical data to show how the UK’s GDP is falling compared to other G8 Nations.

Source: The Guardian, 2022

Now you might think ‘this is quantitative data so it’s objective’ and on that basis no one can argue with what it’s telling us – the U.S. economy is doing VERY WELL compared to most Euro nations, growing more than TWICE as fast is the impression we get.

And after all, this is fair enough – a 2.6% growth rate is more than twice as fast as a 1% or less growth rate!

Same data different scale…

However you might think differently about the above when you see the same data (almost) displayed by the UK Government in this publication: GDP International Comparisons: Key Economic Indicators which features the graph below:

Source: Commons Library 2022

Note that the data is ALMOST the same – except for Britain’s data being different at 0.6% positive rather than negative – the Guardian article was written after the UK Gov report on the basis of the UK Economic growth forecast being downgraded, but everything else is the same.

My point here is that the data above is (almost) the same and yet the graph has been ‘squashed’ compared to the graph showing the same data in The Guardian article – note the scaling is the same – if you look above you can see that the US Bar is twice as high as the EU bars, but the difference APPEARS smaller because it’s not as stretched.

The Guardian achieves its stretched out scale by displaying the bars horizontally rather than vertically – that way there is more room to stretch them out and make the differences appear larger in a visual sense.

And with the UK now in an economic downturn it makes Britain seem further behind compared to other countries than what would have been the case with the more squished presentation in the Government’s version.

But aren’t they both biased…?

In a word yes – someone has to decided the format in which to present the data which is going to skew what people see.

But the reason I’m calling out The Guardian on this is for two reasons:

  1. it’s unusual to display bars horizontally, the standard is vertically, but there’s not way you can stretch out the visualisation vertically without it looking very odd.
  2. The differences are quite small – we are talking 1-2% points of change so having a more squished scale to represent the small differences seems appropriate, The Guardian has chosen to exaggerate these from the original display possible to make them seem larger than they actually are.

Signposting and Related Posts

This material should be of interest to anyone studying Research Methods.

It’s also a useful example of Left Wing bias in the media, most sociologists focus on right wing bias!

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