Tricks of the trade 2
More prevalent versus more likely

Adulterated education

A good teacher makes a great difference.  Reader Richard M drove this point home when he sent in a junk chart posing as educational material. The offending graphic is used by BBC's Skillswise website to teach "Handling data: Graphs and Charts".  Skillswise is an otherwise laudable effort to help adults "improve their basic skills in reading, writing and maths".

Skillswise Even for pros, each question is a challenge.  Question 7 really requires a new pair of glasses.

The entire worksheet is located here.  The use of patterns for shading is especially disconcerting.  The graphic also lacks self-sufficiency as we have trouble comparing countries without referencing the underlying data.  As we discussed before, a good graphic is one in which graphical objects (bars, pies, dots, etc.) illuminate the underlying data; when all the data must be printed next to the objects, the graphic is most likely redundant.

Source: BBC Skillswise website.
 

Comments

Jon Peltier

Wow, what a poor set of tutorials. You've presented the worst of them here, but not the only inappropriate one.

Their temperature by day chart challenges the eye with excessive gridlines, and the text describes the data as continuous, even though it shows only one measurement per day.

Chris Hibbert

What restraint! You didn't even complain that they seem to be using a pie chart to compare independent data points. The chart about GP consultations should be a bar chart, since the point is to compare the countries side-by-side rather than to emphasize that they make up a single whole (they don't.)

Xan Gregg

It's easier to answer the questions once you realize the countries/wedges are ordered by size!

zbicyclist

More proof that just about the only chart more abused than the pie chart is the 3-D pie chart.

Kaiser

Chris - great catch. While I was obsessing with figuring out the sizes of the pieces, the biggest blunder was missed. A pie chart used to present data that aren't proportions.

Doug

My retirement plan website uses pretty much the same technique to show my current investments.

I've always thought the pie chart seemed so lonely and sad next to the key, which contains all the useful data anyway.

Kaiser

Doug: that's exactly what I call self-sufficiency on this blog. If all the data have to be shown anyway for the chart to make sense, then the chart is not self-sufficient, and thus redundant.

sara

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Sara
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Gabor

Yes it's a bad chart. A horizontal bar chart would imho be a more appropriate solution (x-axis = time spent). If you go to the original page, you see that this chart was "inspired" by an 'average reading time' chart where a pie chart makes some sense. The whole is part of a series presenting different chart types, so it had to be a pie chart, damn the usability.
However, I see some upsides. These are worksheets to be printed out and worked on by (adult) pupils and students. Such worksheets are commonly in Black-and-White only. So a B/W print is still legible or at least dicipherable, even from a bad printer. It seems like a conscious effort to avoid colors. Better than to use a color design which then is printed out B/W. I can't totally condone this, as I think there are good reasons for schooling material to stick to B/W, cost of color prints being one. Obviously, B/W design also does not discriminate the colour-blind.
The shading scheme reminds me of tinctures in heraldry, see http://en.wikipedia.org/wiki/Heraldic#Tinctures. The pie chart use is still wrong.

Such a nice justification for B/W design and then the same people go and make a worksheet like this: http://en.wikipedia.org/wiki/Heraldic#Tinctures

unrelated P.S. Is there a simple, old-fashioned e-mail-address available to contact Junk Charts author/Kasier Feng ? I have a really bad chart itching to be sent in.

Gabor

[erratum to my comment above]
Such a nice justification for B/W design and then the same people go and make a worksheet like this: http://www.bbc.co.uk/skillswise/numbers/handlingdata/numericalanalysis/mean/factsheet1.shtml

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