Allen writes:
'You would not question the right of authors to choose words in the text, eg between "has crept up", "has increased", "has rocketed".'
Well, I would -- if the numerical increase was, say, 1 per cent rather than 100 per cent (or v.v.).
That facts only have meaning in the light of context and interpretation does not give one the right to describe them in any old way one likes ...
Julian
Dr Julian Wells
Acting Director of Studies
School of Economics
staff web-page: http://fass.kingston.ac.uk/staff/cv.php?staffnum=287
personal web-site: http://staffnet.kingston.ac.uk/~ku32530
Senior lecturer in economics
School of Economics
Faculty of Arts and Social Sciences
Kingston University
Penrhyn Road
Kingston-upon-Thames
KT1 2EE
United Kingdom
+44 (0)20 8417 2285
________________________________________
From: email list for Radical Statistics [[log in to unmask]] On Behalf Of [log in to unmask] [[log in to unmask]]
Sent: 16 June 2010 23:37
To: [log in to unmask]
Subject: Re: [RADSTATS] How to lie with statistics [was: The state of the nation
Scaling pictures linearly with data is a classic error. It raises the question of whether specific software was used, in which case blame the software writer, or the figures were given to a graphic artist who was just innumerate. I think there are psychology studies (but don't have refs to hand) showing that viewers compare areas in this situation but not exactly. Square root scaling would therefore be better than linear. Had they used pictograms (silhouette of wheelchair), readers would be psychologically comparing volumes and a cube root transformation would be advisable. Making the pies vary in colour and tone exaggerates the difference, particularly between 1997 and 2003.
Note that three discs are used to represent three data items, so the data density (cf Tufte) is very low. This is not necessarily bad; you might deliberately include such a graph to lighten a text-heavy page. Bars would more naturally match the values, and the spacing between bars could scale with the number of years.
The question for the authors is what message they intended the graphic to convey. If it is "alarming growth", they may be justified in adding "stress" rather than "distortion" - the assumption that these figures are "correct" and must therefore be represented with precision is in actuality an assumption. You would not question the right of authors to choose words in the text, eg between "has crept up", "has increased", "has rocketed". My worry with graphics is always that the authors (and proof-reading editors - cf the Radstats comment that two parts of thereport are inconsistent) are not sensitive to the implicit messages in graphs. Too many graphs in publications look like exam scripts - you guess what they're getting at and give credit for effort!
Allan
-----Original Message-----
From: email list for Radical Statistics [mailto:[log in to unmask]]
On Behalf Of Ted Harding
Sent: 16 June 2010 10:40
To: [log in to unmask]
Subject: Re: How to lie with statistics [was: The state of the
On 16-Jun-10 08:02:04, Wells, Julian wrote:
> Yikes! The Cabinet Office people might profitably be directed to the
> ONS house style guide or its predecessor "Plain Figures", not mention
> that old faithful "How to Lie with Statistics" (I see from Wikipedia
> that the latter has been claimed to have sold more copies than any
> other text on statistics).
>
> Julian
I was so struck, looking at the graphic, by the apparent disparity
between the perceived "sizes" of the circles and the associated
numbers that I even wondered if the sizes had been deliberately
fudged! So I did a check. Enlarging the picture and using a ruler,
I got, for the diameters of the circles:
1.2m: 42mm
1.5m: 53mm
1.8m: 64mm
Now:
1.5/1.2 = 1.25 ; 53/42 = 1.26
1.8/1.2 = 1.50 ; 64/42 = 1.52
1.8/1.5 = 1.20 ; 64/53 = 1.21
So pretty close agreement between diameter and value (given that
the edges of the circles were a bit fuzzy anyway).
Which just goes to show (essentially Julian's point) that the eye
is more influenced by relative areas than by relative linear
dimensions. Indeed, attempting to estimate "by eye" the relative
diameters (before using the ruler) I had judged that successive
circles were more like 1.5 times as wide as their predecessors.
And that is in keeping with ratios of areas (1.2^2 = 1.44). A nice
"optical illusion".
Well, now, the Cabinet Office statisticians should of course be
encouraged to make the areas in the right ratios, rather than
the diameters, in order to induce appropriate perceptions.
And then they would have to make diameters (presumably the defining
quantity for producing the graphic) proportional to the square roots
(which might require a coffee break). And then they would have to
explain that somehow. Or not -- the report makes no attempt to explain
the scaling of the circles.
So maybe they wouldn't explain. Then some journalist could do what
I've just done and then report "The Cabinet Office report includes
graphics that deliberately play down the massive increase in
claimants from 1997 to 2009. The increase from 1.2m to 1.8m is
an increase of 50 per cent. The circles increase in size by just
[journalist's synonym for 'only'] 22 per cent."
But what journalist is going to pick up on the apparent exaggeration
that is present in the graphic as presented? Maybe Tim Harford?
So perhaps the C.O. should explain! A simple parenthesis in the
caption (to the better form of the graphic) would do it:
"Figure 3.1: The numbers of working-age Disability Living
Allowance claimants have increased by over 40% since 1997,
from 1.2 million to 1.8 million (areas of circles proportional
to numbers)."
Or is that too abstruse?
But since they've stated the numbers so clearly, why bother with
the graphics?
Well, you sort of can't help it once you've woken up a spreadsheet!
In the memorable words of one of Jasper Carrott's best:
"Q: Why do dogs lick their ****s? A: Because they can."
I think we have a very long way to go before the public understanding
of statistical information is informed by presentations which induce
correct perceptions.
Ted.
--------------------------------------------------------------------
E-Mail: (Ted Harding) <[log in to unmask]>
Fax-to-email: +44 (0)870 094 0861
Date: 16-Jun-10 Time: 10:39:23
------------------------------ XFMail ------------------------------
******************************************************
Please note that if you press the 'Reply' button your
message will go only to the sender of this message.
If you want to reply to the whole list, use your mailer's
'Reply-to-All' button to send your message automatically
to [log in to unmask]
Disclaimer: The messages sent to this list are the views of the sender
and cannot be assumed to be representative of the range of views held by
subscribers to the Radical Statistics Group. To find out more about
Radical Statistics and its aims and activities and read current and past
issues of our newsletter you are invited to visit our web site
www.radstats.org.uk.
*******************************************************
***********************************************************************************
This email and any attachments are intended for the named recipient only. Its unauthorised use, distribution, disclosure, storage or copying is not permitted. If you have received it in error, please destroy all copies and notify the sender. In messages of a non-business nature, the views and opinions expressed are the author's own and do not necessarily reflect those of the organisation from which it is sent. All emails may be subject to monitoring.
***********************************************************************************
This email has been scanned for all viruses by the MessageLabs Email
Security System.
****************************************************** Please note that if you press the 'Reply' button your message will go only to the sender of this message. If you want to reply to the whole list, use your mailer's 'Reply-to-All' button to send your message automatically to [log in to unmask] Disclaimer: The messages sent to this list are the views of the sender and cannot be assumed to be representative of the range of views held by subscribers to the Radical Statistics Group. To find out more about Radical Statistics and its aims and activities and read current and past issues of our newsletter you are invited to visit our web site www.radstats.org.uk. *******************************************************
This email has been scanned for all viruses by the MessageLabs Email
Security System.
******************************************************
Please note that if you press the 'Reply' button your
message will go only to the sender of this message.
If you want to reply to the whole list, use your mailer's
'Reply-to-All' button to send your message automatically
to [log in to unmask]
Disclaimer: The messages sent to this list are the views of the sender and cannot be assumed to be representative of the range of views held by subscribers to the Radical Statistics Group. To find out more about Radical Statistics and its aims and activities and read current and past issues of our newsletter you are invited to visit our web site www.radstats.org.uk.
*******************************************************
|