[R) Bland Altman plot (was: [R] paste ?)
maj at waikato.ac.nz
Wed Apr 26 07:45:22 CEST 2000
The idea of comparing the variances of two variables X and Y by looking at
the correlation of
X + Y with X - Y
seems to go back to Pitman (1939) A note on normal correlation, Biometrika,
31, pp 9-12.
I havn't seen the paper myself but I presume that the essentials are
summarized in Cox & Hinkley (1974) pp 140, 141. These days, of course, we
are keener on plots than formal tests.
I discovered all this around 1977 when I was interested in the case where X
and Y were measurements of quantities like %fat in cheese obtained by two
different methods or by two different labs.
At 10:35 PM 25-04-00 +0200, Peter Dalgaard BSA wrote:
>"Christophe Declercq" <cdeclercq at nordnet.fr> writes:
>> > Secondly, I'm curious about the history of this kind of plot.
>> > I've only heard it called a "Tukey mean difference" plot, (and
>> > Trellis graphics has a function, tmd(), that does it, but no one
>> > knows about it...). Does anyone know who invented it?
>> Martin Bland and Doug Altman introduced it in their very successful 1986
>> paper in The Lancet (which has become a 'Citation Classic') :
>However, as so many other CTs, I don't think they actually invented
>the procedure... Plotting residuals vs. fitted values to avoid
>correlation, and warnings against the fallacy of plotting a difference
>against one of the terms have certainly been around long before '86.
>The Lancet paper is not really an introduction of a new method, rather
>it is a polemic paper against the widespread practise of publishing
>correlation coefficients as measures of agreement between two methods.
>[Of course, since people in the medical profession treats Lancet
>papers as The Law, and vocal statisticians like Altman as demigods,
>one occasionally meets people trying to use the Bland-Altman plot for
>comparing measurements on completely different scales!]
>> Bland JM, Altman DG. Statistical methods for assessing agreement between
>> two methods of clinical measurement. Lancet 1986; i: 307-310.
> O__ ---- Peter Dalgaard Blegdamsvej 3
> c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
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Dr Murray Jorgensen http://www.stats.waikato.ac.nz/Staff/maj.html
Department of Statistics, University of Waikato, Hamilton, New Zealand
*Applications Editor, Australian and New Zealand Journal of Statistics*
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