Notice: On March 31, it was **announced** that Statalist is moving from an email list to a **forum**. The old list will shut down on April 23, and its replacement, **statalist.org** is already up and running.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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 10:43:55 -0400 |

Ah yes, I stand corrected. Nick On 10/20/2011 10:39 AM, Austin Nichols wrote:

Nick-- The poster (Andrew Wade) has survey data, though. In survey data, using a cluster-robust variance estimator, the two are identical. webuse nhanes2, clear svy: reg bpsystol black, sformat(%7.6f) qui svy: mean bpsystol, over(black) lincom _b[1]-_b[0], sformat(%7.6f) On Thu, Oct 20, 2011 at 10:00 AM, Nick Winter<nwinter@virginia.edu> wrote:There is a subtle difference between -svy: reg- and -svy: mean- followed by -lincom-. The former corresponds to a t-test with the assumption that the variances in the two populations are equal; the latter corresponds (almost exactly) to a t-test without that assumption. The "almost exactly" is due to a difference in calculation of degrees of freedom. 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.* * 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/

**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>

**Re: st: Testing whether two estimated survey means are statistically different***From:*Nick Winter <nwinter@virginia.edu>

**Re: st: Testing whether two estimated survey means are statistically different***From:*Austin Nichols <austinnichols@gmail.com>

- Prev by Date:
**Re: st: Propensity Score Matching, fixing date variable when matching using psmatch2** - Next by Date:
**st: RE: looping a regression, exporting the graphs** - Previous by thread:
**Re: st: Testing whether two estimated survey means are statistically different** - Next by thread:
**Re: st: Testing whether two estimated survey means are statistically different** - Index(es):