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st: RE: pctile, xtile methods -- correction


From   Joly.Patrick@ic.gc.ca
To   statalist@hsphsun2.harvard.edu
Subject   st: RE: pctile, xtile methods -- correction
Date   Mon, 9 Jun 2003 08:42:45 -0400

I wrote
> 2. Possibly inaccurate percentiles
> ==================================
> 
> In the example above, the 7th percentile is 8.  But according to the
default
> method, x_7 should be given by the mean of x[6] and x[7] because P =
> _N*(7/100) = 7, the smallest index i > P is i = 8 and (i-1) = P.  This
> implies that x_p should be 7.5 for p = 7.


I should have written,

2. Possibly inaccurate percentiles
==================================

In the example above, the 7th percentile is 8.  But according to the default
method, x_7 should be given by the mean of x[7] and x[8] because
                                             ^        ^
P = _N*(7/100) = 7, the smallest index i > P is i = 8 and (i-1) = P.  This
implies that x_p should be 7.5 for p = 7.



Patrick Joly
joly.patrick@ic.gc.ca
pat.joly@utoronto.ca
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