```Date: Mon, 26 Apr 2004 08:39:43 -0400 Reply-To: Susie.Li@US.SANOFI.COM Sender: "SAS(r) Discussion" From: Susie Li Subject: Re: Percentile for a specific value against an empirical distribution Content-Type: text/plain; charset=us-ascii 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? Susie Li Sales Operations, Sanofi-Synthelabo, Inc. 90 Park Ave, New York, NY 10016 (212)551-4385 susie.li@us.sanofi.com __________________ Susie.Li@US.SANOFI.COM wrote: > How does PROC UNIVARIATE handle ties in calculating percentiles? Actually, in the computations for just the percentiles (and other quantiles), the ties do not matter. The values get treated just like every other data point. What this means in practice is that if the Kth percentile would be the weighted average of values Xj and Xj+1 (PCTLDEF=1), and these are equal (they are tied), then the percentile value is still their average.. which is the same as their (tied) value. Ties are more problematic in the computation of a variety of nonparametric statistical methods, but they just don't cause a problem when we compute the percentiles. In fact, if we're doing percentiles by hand, they just make things easier. HTH, David -- David Cassell, CSC Cassell.David@epa.gov Senior computing specialist mathematical statistician Important: The Information in this e-mail belongs to Sanofi-Synthelabo Inc., is intended for the use of the individual or entity to which it is addressed, and may contain information that is privileged, confidential, or exempt from disclosure under applicable law. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution, or use of, or reliance on, the contents of this e-mail is prohibited. If you have received this e-mail in error, please notify us immediately by replying back to the sending e-mail address, and delete this e-mail message from your computer. ```

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