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From |
Maarten buis <maartenbuis@yahoo.co.uk> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: Re: Examining sampling distribution |

Date |
Tue, 17 Nov 2009 14:49:36 +0000 (GMT) |

--- Babak Oskooei wrote: > My question is how I can add a curve of Chi2 distribution > with 1 df to the histogram of the sampling distribution of > my statistic. --- On Tue, 17/11/09, Nick Cox wrote: > But there is a much, much, much better way for you to > proceed. -qchi- and -pchi- are built-in commands for > your exact purpose I agree with Nick that a histogram with a theoretical curve overlaid is not the best way to go. An alternative that may look more familiar is the hanging rootogram. (examples of these graphs can be seen here: http://www.maartenbuis.nl/software/hangroot.html ) The idea behind the hanging rootogram is that the bars "hang" from the theoretical distribution rather than "stand" on the x-axis. This way deviations from the theoretical curve are visible as deviation from a horizontal line, which makes it much easier to spot patterns in these deviations than in the regular histogram where they are represented as deviations from a curve. Moreover, by using the square root scale for the frequencies, any patterns in the tails become more visible. In the current version the Chi square distribution is not implemented, nor is it possible to fix the df of the theoretical distribution to 1, as you requested. I just implemented both options and sent the updated files to Kit Baum so he can put it on SSC. So that should be available shortly. Hope this helps, Maarten -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * 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/

**References**:**st: RE: Re: Examining sampling distribution***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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