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From |
"Michael N. Mitchell" <Michael.Norman.Mitchell@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: interpreting margins results |

Date |
Mon, 09 Aug 2010 22:47:19 -0700 |

Dear Richard

I hope this helps, Michael N. Mitchell Data Management Using Stata - http://www.stata.com/bookstore/dmus.html A Visual Guide to Stata Graphics - http://www.stata.com/bookstore/vgsg.html Stata tidbit of the week - http://www.MichaelNormanMitchell.com On 2010-08-09 9.01 PM, Richard J Stoll wrote:

I am using Stata/SE 11.1 on a PC. I would appreciate help on interpreting the output from the margins command. I have read the documentation and looked around for examples on the web and cannot find an example in which the calculated margin is significant for one (or some) values of the variable, but not for others. My question is how to interpret such a finding. Note: what follows is taken from a real dataset I am using, but the model shown below is simpler than what I am doing. Here is the regression command and results (note: I have chopped the right side of the results so they won't wrap across lines; I always find that hard to read). . reg dmnetsupp i.d1982##c.lpchgdef Source | SS df MS -------------+------------------------------ Model | 1148.21514 3 382.73838 Residual | 4337.83844 33 131.44965 -------------+------------------------------ Total | 5486.05358 36 152.390377 ----------------------------------------------------- dmnetsupp | Coef. Std. Err. t P>|t| -------------+--------------------------------------- 1.d1982 | -6.62355 4.204622 -1.58 0.125 lpchgdef | -.2784506 .210933 -1.32 0.196 | d1982#| c.lpchgdef | 1 | -.235843 .3527 -0.67 0.508 | _cons | 6.204468 3.459617 1.79 0.082 ----------------------------------------------------- And then I use the following margins command, followed by the results (again I have chopped the right side to avoid wrapping lines): . margins i.d1982 Predictive margins Number of obs = 37 Model VCE : OLS Expression : Linear prediction, predict() ------------------------------------------------------ | Delta-method | Margin Std. Err. z P>|z| -------------+---------------------------------------- d1982 | 0 | 5.590552 3.472332 1.61 0.107 1 | -1.552974 2.256145 -0.69 0.491 ------------------------------------------------------ How would you discuss the difference in the z-scores/probabilities for the two margins values of d1982? Thanks for your help. ------------------------------------------------------------------- Richard J. Stoll * Albert Thomas Professor of Political Science * Rice University * Political Science MS 24 * P.O. Box 1892 * Houston TX 77251-1892 * stoll@rice.edu * 713-348-3362 * FAX: 713-348-5273 * * 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/

* * 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: interpreting margins results***From:*Richard J Stoll <stoll@rice.edu>

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