Date: Mon, 26 Apr 2004 08:39:43 -0400
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: Susie Li <Susie.Li@US.SANOFI.COM>
Subject: Re: Percentile for a specific value against an empirical
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In pharma, we are used to pctldef=10 (pctltile 1-10=decile 1, pctltile
11-20=decile 2,..., pctltile 91-100=decile 10). As the result, there are
many points tied on the decile boundaries. We promote them to the higher
of the deciles in general.
What would be the easiest way to handle such 'DECILING', essentially a
collapsing of percentiles?
Sales Operations, Sanofi-Synthelabo, Inc.
90 Park Ave, New York, NY 10016
> How does PROC UNIVARIATE handle ties in calculating percentiles?
Actually, in the computations for just the percentiles (and other
the ties do not matter. The values get treated just like every other
point. What this means in practice is that if the Kth percentile would
the weighted average of values Xj and Xj+1 (PCTLDEF=1), and these are
(they are tied), then the percentile value is still their average..
the same as their (tied) value. Ties are more problematic in the
of a variety of nonparametric statistical methods, but they just don't
a problem when we compute the percentiles. In fact, if we're doing
by hand, they just make things easier.
David Cassell, CSC
Senior computing specialist
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