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From |
Nick Winter <nwinter@virginia.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Testing whether two estimated survey means are statistically different |

Date |
Thu, 20 Oct 2011 10:00:08 -0400 |

Leaving aside -svy-, we can see the slightly different standard errors: sysuse auto reg mpg foreign ttest mpg, over(foreign) mean: mpg, over(foreign) lincom _b[Domestic]-_b[Foreign] ttest mpg, over(foreign) unequal - Nick Winter On 10/20/2011 4:58 AM, Maarten Buis wrote:

On Wed, Oct 19, 2011 at 11:33 PM, Andrew Wade<awade@allenconsult.com.au> wrote:Presumably the regression approach, where you have a single dummy for the sub-population, will be identical (or near identical) to: - estimating svy: mean with over command (ie. mean for sub-population, and not in sub-population). - lincom after svy: mean. Or could the regression approach be applied, whereby you suppress the constant term? Wouldn't this alternate regression approach be closer to what I'm after?In terms of coefficients, yes, but in terms of test, no. These two test are truely equivalent, meaning they contain exactly the same information and nothing is gained by chosing one over the other. Think of it this way: You can say Adam has 3 and Berta has 2 more (constant is 3 and the coefficient of Berta is 2) or you can say Adam has 3 and Berta has 5 (suppress the constant and add dummies for Adam and Berta). The two statements contain exactly the same information. The only reason for prefering one over the other is ease of explanation. Sometimes we have hypotheses or traditions within a (sub-)discipline which would make it easier for your audience to understand one parameterization over the other. 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/

-- -------------------------------------------------------------- Nicholas Winter 434.924.6994 t Associate Professor 434.924.3359 f Department of Politics nwinter@virginia.edu e University of Virginia faculty.virginia.edu/nwinter w S385 Gibson Hall, South Lawn * * 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: Testing whether two estimated survey means are statistically different***From:*Austin Nichols <austinnichols@gmail.com>

**References**:**Re: st: Testing whether two estimated survey means are statistically different***From:*"Andrew Wade" <awade@allenconsult.com.au>

**Re: st: Testing whether two estimated survey means are statistically different***From:*Maarten Buis <maartenlbuis@gmail.com>

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