Visualisation: Visual representations of data and information
Visualisation: Visual representations of data and information

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

Visualisation: Visual representations of data and information

3.2 Cheating with bar charts

Bar charts are subject to various sorts of ‘creative’ use. For example, the bar chart in Figure 7 shows huge differences in the four charted quantities, does it not?

Or maybe not – see also Figure 8.

A bar chart
Figure 7 The values 235, 255, 270, 240 shown on a bar chart
An alternative bar chart
Figure 8 The values 235, 255, 270, 240 shown on a bar chart, but this time with the vertical axis starting at zero

Many spreadsheet packages that are used to create charts also allow the user to employ shapes other than simple bars when constructing a bar chart. This may not be a good thing.

For example, chart widgets like the ones shown in Figure 9 are available from Google Charts. As well as being potentially misleading because it’s not immediately clear where zero lies (the train chart ranges from 200 to 270 whereas the piles of money chart ranges from 0 to 270), the imagery can also be a distraction. Where different 2D shapes are used for the bars, the area of the shape may change out of proportion with the height or length of the ‘bars’, which would mislead the reader at a perceptual level. Where 3D imagery is used, the reader can be confused (even unconsciously) about whether the height or the volume of the chart is what is significant.

Data represented by the length of a goods train and by piles of bank notes
Figure 9 (a) The values 235, 255, 270 and 240 represented by shapes. Here the different lengths of the two shapes used can mislead (as can the fact the ‘bars’ do not start at zero). (b) The same values represented by piles of money. Here the fact that there is a 3D representation is misleading: is it height or volume that represents the four values?
T215_1

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371