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From |
"Scott Merryman" <smerryman@kc.rr.com> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: Re: Re: t-tests for differences in means using pweights |

Date |
Thu, 26 Jun 2003 20:22:33 -0500 |

----- Original Message ----- From: <sharkey@fas.harvard.edu> To: <statalist@hsphsun2.harvard.edu> Sent: Thursday, June 26, 2003 10:33 AM Subject: st: Re: t-tests for differences in means using pweights > I don't think my original posting was clear enough. What I have are two unique > samples, one from the first wave of a survey and the other from the next wave. > In each wave respondents were asked the same question, and I'm looking at > aggregate means on this question for each wave of the survey. I'm trying to > determine whether the difference in the mean value of the variable among > respondents in the first wave is significantly different from the mean among > respondents in the second wave (after weighting the responses with pweights). > The problem is that the samples are unique, so I can't use the "svymean" > or "svylc" commands, but I also can't use the "ttest" command b/c it does not > accept pweights. I hope this is clearer than the first post below, and again I > would appreciate any thoughts. Thanks in advance. > > Pat Sharkey > Doctoral student in Sociology and Social Policy > Harvard University How about using a dummy variable and svyreg. Using the auto dataset, suppose sample 1 is the price of car domestic cars and sample 2 is the price of foreign cars and the sampling weight is the weight variable. . use "C:\Stata8\auto.dta", clear (1978 Automobile Data) . svyset [w=weight] (sampling weights assumed) pweight is weight . svyreg price for Survey linear regression pweight: weight Number of obs = 74 Strata: <one> Number of strata = 1 PSU: <observations> Number of PSUs = 74 Population size = 223440 F( 1, 73) = 0.13 Prob > F = 0.72 13 R-squared = 0.0015 ---------------------------------------------------------------------------- -- price | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+-------------------------------------------------------------- -- foreign | 298.4742 833.3626 0.36 0.721 -1362.415 1959.363 _cons | 6500.577 503.7304 12.90 0.000 5496.644 7504.51 ---------------------------------------------------------------------------- -- The t-stat on the dummy variable tests if the mean price of foreign cars is equal to the mean price of domestic cars. So, the null hypothesis of Ho: mean(Domestic) - mean(Foreign) = 0 can be rejected at usual significance levels. Scott * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: t-tests for differences in means using pweights***From:*Patrick Thomas Sharkey <sharkey@fas.harvard.edu>

**st: Re: t-tests for differences in means using pweights***From:*sharkey@fas.harvard.edu

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