Oops, that should read 99.2%, not 99.7% .
m.p.
Marcello Pagano wrote:
What Ted said is quite correct, but you can also exercise your
imagination and notice that if you have normal data, then the expected
value of the interquartile range is 1.34 sigma (just reading from the
normal tables). Thus, in this case, the adjacent values are estimates
of mean plus or minus twice the interquartile range, or mean plus or
minus 2.64 sigma. That means that you should have almost all your data
(99.7%) between the two adjacent values.
m.p.
S�ren O'Neill wrote:
Thank you very much for your reply - is there a reference you can give
me, that explains the reasoning behind these adjacent values -
personally I rely mostly on the book Practical Statistics for Medical
Research by D. Altman and I cant seem to find any reference to
'adjacent values' therein ... Also the Stata Users guide and reference
manuals seem to come up short ...
Kind regards
Soren
On Monday 05 July 2004 23:32, Ted Anagnoson wrote:
The adjacent values separate the outliers from the rest of the data.
They
are the 25th or 75th percentiles plus 1.5 times the Inter-Quartlile
range,
which is the distance between the 25th and 75th percentiles.
However, the
adjacent value indicated on the graph, by convention, is "rolled
back" to
an actual data point, so that there is always real data underneath the
adjacent value.
So the adjacent values are not actually percentiles....but "adjust"
to the
characteristics of the data.
Ted Anagnoson
California State University Los Angeles
At 10:46 PM 7/5/04 +0200, you wrote:
The box and whiskers graph illustrates the median value (with a
line), the
25%
and 75% centiles (with a box) and the adjacent values (with the
whiskers)
... but what are the adjacent values? 2� and 97� centiles or ... ???
--
S�ren O'Neill, kiropraktor
[email protected]
tel. 6362 1906
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
--
______________________________________________________________________
Marcello Pagano
Biostatistics Department Tel: 1-617-432-4911
Harvard School of Public Health Fax: 1-617-739-1781
655 Huntington Avenue email:[email protected]
Boston, MA 02115 http://biosun1.harvard.edu/~bio200
USA
eppur si muove
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
