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RE: Antwort: st: RE: RE: graph for propensity scores


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: Antwort: st: RE: RE: graph for propensity scores
Date   Wed, 13 Apr 2005 11:26:20 +0100

Sorry, but I think your supposed justification for 
upwards and downwards designs misses my comment 
completely. For example, an upwards and upwards 
design is based on exactly the principle you 
cite, so common support does not dictate 
graphical design. 

My comment is based on graphical statistics literature 
focusing on what kinds of comparison are easy 
and effective. "The elements of graphing data" 
by William S. Cleveland (full reference in 
the Stata manuals) leads to some literature. 

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

Hans J. Baumgartner
 
> That?s exactly the reason why propensity scores should be 
> shown in the 
> ?upwards and downwards? design, since the graph shall show that both 
> groups do have a common support area. 
> 
> I?ll check the reference anyway. 
 
> > Upwards and downwards designs appear popular 
> > for no good reason. In effect the reader is 
> > expected to be able to pick up one length, 
> > transfer it and superimpose it, all in one's
> > head, upon another length. Why this should be easier 
> > or more effective than comparing juxtaposed lengths 
> > beats me. 
> > 
> > The same issue arises with left and right 
> > (side-by-side) designs such as population 
> > pyramids. 
> > 
> > In each case, small and subtle differences 
> > could easily be of interest or importance. 
> > 
> > The problem with histograms is naturally the 
> > loss of detail produced by binning. Often 
> > this is unimportant but frequently a researcher
> > does want to be sure that is so. 
> > 
> > To compare two sets of values qua distributions, 
> > -qqplot- is pretty nearly an optimal plot. To 
> > compare them as paired values, there are several 
> > good methods. A fairly lengthy discussion with 
> > references is given in 
> > 
> > Graphing agreement and disagreement. 
> > Stata Journal 4(3): 329--349 (2004)

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