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RE: st: RE: Re: Weighted number of observations


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: Re: Weighted number of observations
Date   Tue, 3 Aug 2004 22:16:51 +0100

No, sorry, but I think you are missing 
two points here. 

Easier one first: the expression "passing the buck" 
was, as you probably realise, my 
attempt to leaven an otherwise dull 
posting. More seriously, the division 
of labour whereby -tabstat- organises
and displays what is produced by 
-summarize- internally is excellent 
from all points of view. There is 
no reason at all to change it. If 
-tabstat- doesn't do something, 
and a different program is needed, 
that's a different matter. The 
rationale of -tabstat- is to act 
as a wrapper for, and thus to be 
totally consistent with,  what 
-summarize- calculates. To get
-tabstat- to do something different, 
or extra, would in my view be bad 
program design, modulo a few arguable 
details (e.g. cv is just a minor 
extension of what -summarize- does). 

On the original question, I maintain 
that Stata is working consistently 
with the documentation, but I do 
agree that the latter could be
tweaked to make it clearer. A key 
principle is that whenever a sum 
of weights is being used, what that
sum of weights is should be accessible
in some way, and Stata satisfies this
criterion. 

Nick 
n.j.cox@durham.ac.uk 

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Richard
> Williams

> 
> At 03:34 PM 8/3/2004 +0100, Nick Cox wrote:
> >This isn't a -tabstat- issue as such. -tabstat-
> >just passes the buck to -summarize-, which
> >behaves in the same way.
> >
> >The issue is delicate, but hinges, I surmise,
> >on this distinction. When -summarize- (e.g.) _uses_
> >the sum of the weights, it rescales first.
> >As quoted, [U] 14.1.6 includes the expression
> >"when it uses them", which thus appears not
> >ornamental, but crucial.
> >
> >When -summarize- _displays_ the sum of the
> >weights, it displays the unscaled sum.
> 
> Good point, although it still leaves open the question of why 
> it behaves 
> this way.  A long-standing oversight or bug?  Sound 
> statistical practice? 
> (If so, it wouldn't be the first time Stata has surprised me 
> by not doing 
> what I expected, and then having it turn out that Stata was 
> right.)  Should 
> -tabstat- be modified so it doesn't just pass the buck to -summarize-?

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