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Re: st: Spss's aggregate vs stata's collapse.


From   Ulrich Kohler <kohler@wzb.eu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Spss's aggregate vs stata's collapse.
Date   Wed, 13 Apr 2011 15:19:56 +0200

Am Mittwoch, den 13.04.2011, 12:13 +0100 schrieb Brendan Halpin:
> On Wed, Apr 13 2011, Amadou DIALLO wrote:
> 
> > Brendan, Uli,
> > Thanks for answers. Yes, it has to do with weights. Removing it yields
> > same results. Apparently SPSS rounds non-integer weight to the nearest
> > integer (the total weighted frequency, not individual weights (sic!):
> > www.spsstools.net/Tutorials/WEIGHTING.pdf
> 
> SPSS is doing the wrong thing here, then. 
> 
> > I've tried Brendan's solution but this is not working. So far, I can't
> > duplicate results and am stuck. Will continue checking.
> 
> If you really need to duplicate the results, you need to replicate
> SPSS's "error". It may be enough to round the weight yourself. 

I know that this is not a SPSS list, however I'm still puzzled about
what "rounding to the nearest integer" here really means. If a sampling
weight has been rescaled such that the sum of weights is equal to the
number of observations, there will be quite a number of weights below
0.5. Are they "rounded" to 0 then, meaning to drop them from the
analysis? Or is zero not an integer value? Or do we use, the geometric
mean or  harmonic mean between two subsequent numbers as the threshold
for rounding, or what. 

SPSS = Some petty Statistical Software?

Uli



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