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From |
Maarten Buis <maartenlbuis@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: ZOIB procedure |

Date |
Tue, 20 Sep 2011 11:41:39 +0200 |

--- On Tue, Sep 20, 2011 at 11:20 AM, Prerna S wrote: > As a follow-up question, the statistical significance of the marginal > effects differs from the statistical significance of the zoib > regression estimates. How does one explain this difference? And in > explaining results, does one choose zoib results or marginal effects? I would go for marginal effects. You can interpret exponentiated coefficients as odds ratios (for being an exact 0 or an exact 1, depending on the equation) and relative proportion ratios given one is not an exact 0 or 1 (see -help betafit- for an example on relative proportion ratios). The problem is that these are conditional effects while you probably want the effect on the unconditional expected proportion, and these ratios are non-standard so they need a lot of explaining. I can think of two reasons why the statistical significance differs, and they are all a variation on the point that they represent different null-hypotheses: 1) The parameters represent relative effects (ratios), while marginal effects represent absolute effects (differences). 2) The marginal effects combine the effects on all two or three equations of the model. -- 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/

**Follow-Ups**:**Re: st: ZOIB procedure***From:*Prerna S <maruiprerna@gmail.com>

**References**:**st: ZOIB procedure***From:*Prerna S <maruiprerna@gmail.com>

**Re: st: ZOIB procedure***From:*Maarten Buis <maartenlbuis@gmail.com>

**Re: st: ZOIB procedure***From:*Prerna S <maruiprerna@gmail.com>

**Re: st: ZOIB procedure***From:*Prerna S <maruiprerna@gmail.com>

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