Misleading Graph

Thursday, 04 August 2011 | 2 Comments

I’m not trying to present a view, either way, on the carbon tax being debated in Australia. But those against the carbon tax seem to be providing some good fodder for the maths classroom.

Have a look at this TV advertisement:

Australian Trade & Industry Alliance Carbon Tax Ad from ACCI on Vimeo.

When looking at the topic of Data Representation with Stage 4 students, we cover “misleading graphs”. That is where the creator of the graph constructs the graph poorly to bias one viewpoint. (See the NSW BOS 7-10 Syllabus: “analyse graphical displays to recognise features that may cause a misleading interpretation eg displaced zero, irregular scales” DS4.1). In addition to the examples listed in the syllabus, I also talk about the misuse of area.

What are the two problems with the graph in the advertisement above?
How do these problems support (or not) the case being put forward in the advertisement?

It would be a simple exercise for students to create this graph correctly.

Posted in • Lesson Idea • Graphs | Short URL: http://mths.co/2246

Comments

Adam Bevan on 04 August 11 at 07:17 AM #

I was thinking that myself Simon when I saw it on the Gruen Transfer last night. I was surprised they did not pick up on it. Good lesson idea. Not only the width of the bars are misleading the height of the bars are not correct either. The column for Australia should be even higher than what it is. The choice of orange is worth discussing "Orange increases oxygen supply to the brain, produces an invigorating effect, and stimulates mental activity."

author

Simon Job on 04 August 11 at 10:29 AM #

Thanks Adam for identifying those two errors - that is what I picked up. It's strange that they made the Australia bar wider - to emphasise it. Yet, if they had a consistent scale (it goes up 1,2,3,4,5,10,15...) the difference between the two columns heights would have been greater.

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Simon Job — eleventh year of teaching maths in a public high school in Western Sydney, Australia.
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