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From |
Steve Samuels <sjsamuels@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: weighted t-test |

Date |
Wed, 18 Jan 2012 21:06:59 -0500 |

1. Use [pw = ] for survey data. And, if there are strata and clusters, they should appear in the -svyset- statement. 2. your -svy reg- statment would give you the same gender difference if you had typed: -svy: reg nr_pos i.gender- 3. Your question is fuzzy. Suppose the population means of x for males and females are: males: m1 = 40 females: m2 = 60 Then the difference is m2 - m1 = 20 If m is the population mean, then m1 < m < m2, because m is a weighted mean of the males and females, weighted by their proportions in the population. If the weights are 50% and 50%, then m = 50 in our case. Thus you can see that if m1 = m2, then m = m1 and m= m2. If m1 < m2 the m1< m and m2>m. If m1> m2 then m1 > m and m2 < m. Steve sjsamuels@gmail.com It statesFirst of all, estimates and tests are about the population, not the sample, Are you asking if mean_1 - mean_2 is the same as the population mean-? If so, the answer is "no". On Jan 18, 2012, at 9:26 AM, rosa wrote: Hi, I want to perform a weighted t-test using survey data. Given I cannot apply the 'ttest' command together with 'svy', I am using the 'lincom' command (as learned in stata's FAQ). My question is: Is testing the difference between different groups (x1-x1) the same as testing whether the difference between groups is significantly different than the average of the sample? This is what I've done: svyset count [iw= WEEGFACT] tab gender, gen(x) sum x1 x1 svy: reg nr_pos x1 x2, nocons lincom x1-x2 Thank you in advance. Rose * * 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: weighted t-test***From:*rosa <rosahh.rosa@gmail.com>

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