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From | Nick Cox <njcoxstata@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: q-q plots, theoretical distribution with values higher than the sample's cutoff point |
Date | Wed, 18 Jul 2012 17:48:37 +0100 |
These programs are in package -qpfit- on SSC. The word "problem" here is ambiguous. My bias is to guess that your data don't follow any of these distributions very well and the graphs are telling you that. -su dec_ae, detail- would tell us a bit more. Nick On Wed, Jul 18, 2012 at 5:13 PM, Lucia Latino <Latino@economia.uniroma2.it> wrote: > I am having some problems with the q-q plots for Dagum, gb2, lognormal and > Singh-Maddala distributions using programs written by Nick Cox. > > After having fit the distribution (e.g. lognfit dec_ae, svy), I run the > command for the q-q plot (e.g. qlogn dec_ae [pweight=iwght]). > > I repeat the same procedure for the other distributions (Dagum, gb2 and > Singh-Maddala). All the plots show a strange behavior: in all the qq-plots, > the points follow a strongly nonlinear patters. At the beginning they follow > the 45 degree line, then they depart significantly from the 45 degree line > and become flat around the value 10,000, which is the max value for dec_ae. > > What does it mean? Why the theoretical distribution takes value higher than > 10,000? > > I hope I was clear enough. I wish I could show you the plots, but I > understood I cannot attach them. > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/