I disagree.
Of course we should choose language according to the audience but
redefining terms is not the solution. Nor is accepting the wrong
usage instead of the technical (ie correct) definition just because
it is common in the wider world. We don't do that, for example, with
"random" to take one key example, and nor should we with quartile (etc).
I know that this usage is common in my field of medical research [1]
and also even by statisticians. Does that make it OK?
I believe that statisticians should use terms correctly in
professional discussions and in general outside too. (In the right
context technical terms are not jargon.) Thus there are 3 quartiles
(one being the median), 4 quintiles, and so on. These are specific
examples of quantiles. Growth charts show multiple centiles against
which individuals are judged. One might be at (or above) the 70th
centile for example. It is common to describe the distribution of a
skewed variable using the median and (lower and upper) quartiles -
clearly these are specific values. The term interquartile range
becomes meaningless if we redefine the quartiles as the quarters.
Likewise quantile regression.
Confusion will surely arise if we use one word to mean two different
things, and it seems crazy when we have two different words already.
What is vague about the "top quarter"? Or perhaps the "top 25%"? If
there is no simple way to describe those between the 3rd and 4th
deciles, then call them bands or some other term. That is not a good
reason to redefine what is a perfectly good word. One possibility is
to call them "decile groups" - "groups of the population defined by
the decile points". See http://www.dwp.gov.uk/asd/hbai/glossary.html
Doug
Reference:
[1] Altman DG, Bland JM. Quartiles, quintiles, centiles and other
quantiles. BMJ 1994;309:996.
At 21:06 14/10/2008, John Sorkin wrote:
>Perhaps better usage would entail using the term upper half, third,
>quarter, fifth, sixth, etc. Quartile constitutes jargon, something
>we all use too often, but should strive to avoid.
>John
>
>John David Sorkin M.D., Ph.D.
>Chief, Biostatistics and Informatics
>University of Maryland School of Medicine Division of Gerontology
>Baltimore VA Medical Center
>10 North Greene Street
>GRECC (BT/18/GR)
>Baltimore, MD 21201-1524
>(Phone) 410-605-7119
>(Fax) 410-605-7913 (Please call phone number above prior to faxing)
>
> >>> Murray Jorgensen <[log in to unmask]> 10/14/2008 3:46 PM >>>
>Here in NZ all schools are classified into 10 deciles and we often hear
>talk of a "decile 3" or a "decile 10" school. I have never heard of
>anyone being pulled up over this usage.
>
>Murray Jorgensen
>
>Allan Reese (Cefas) wrote:
> > I was pulled up recently for using the phrase "top quartile" to define a
> > quarter of a sample. Statistical dictionaries appear to support my
> > critic, defining the quartile as the point estimate of the percentile.
> > However, I feel it's a long-established extension of meaning to refer to
> > the parts of the sample or population. For example, this from the
> > Guardian 2003:
> >
> > "... They quote Alison Wolf, of the London School of Economics, to show
> > that when only 10% of the population have degrees, someone in the top
> > 25% of the ability range will still have plenty of job opportunities and
> > it is a rational decision not to bother with university. But once more
> > than 50% of the population holds a higher education qualification, the
> > same employer that was targeting the top quartile of the population in
> > terms of ability will now make the assumption that they require a
> > graduate."
> >
> > Do you agree with my usage, or think it sloppy and wrong? If the
> > latter, what word does describe the subset? The "top quarter" seems to
> > me vague and ambiguous.
> >
> >
> >
> > Comments to me, and I'll summarize later.
> >
> > Allan
> >
> >
> >
> >
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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
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