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| From | Nick Cox <njcoxstata@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | Re: st: means compairison with weights and unequal variance |
| Date | Mon, 21 Nov 2011 09:34:16 +0000 |
ttesti `=N1[1]' `=av1[1]' `=sd1[1]' `=N2[1]' `=av2'[1] `=sd2[1]', unequal On Mon, Nov 21, 2011 at 9:33 AM, Nick Cox <njcoxstata@gmail.com> wrote: > This would work. But it is in no sense superior to John's original. > > sysuse auto, clear > sum mpg if foreign [aw=weight] > gen N1 = r(N) > gen av1 = r(mean) > genl sd1 = r(sd) > > sum mpg if !foreign [aw=weight] > genl N2 = r(N) > gen av2 = r(mean) > gen sd2 = r(sd) > > ttesti `=N1[1]' `=av1[1]' `=sd1[1]'' `=N2[1]' `=av2'[1] `sd2[1]', unequal > > The [1] subscripts are possibly superfluous; I have not tested this. > > > On Mon, Nov 21, 2011 at 9:09 AM, Nick Cox <njcoxstata@gmail.com> wrote: >> The syntax ` ' only de-references local macro names. Once you change >> the syntax as you did, the --ttesti- call reduces to >> >> ttesti, unequal >> >> which makes no sense. There is no reason to change it anyway. >> >> Nick >> >> On Mon, Nov 21, 2011 at 9:02 AM, David Ashcraft >> <ashcraftd@rocketmail.com> wrote: >>> John, >>> >>> I am trying to implement the code but replacing local with gen. Why I am not getting the same result, if I use gen rather than local? >>> >>> David >>> >>> >>> ----- Original Message ----- >>> From: John Luke Gallup <jlgallup@pdx.edu> >>> To: statalist@hsphsun2.harvard.edu >>> Cc: >>> Sent: Monday, November 21, 2011 8:40:40 AM >>> Subject: Re: st: means compairison with weights and unequal variance >>> >>> Barbro, >>> >>> A simple alternative is to calculate the means and standard deviations for each group using -summarize- with weights, and then run -ttesti ..., unequal-: >>> >>> sysuse auto, clear >>> >>> sum mpg if foreign [aw=weight] >>> local N1 = r(N) >>> local av1 = r(mean) >>> local sd1 = r(sd) >>> >>> sum mpg if !foreign [aw=weight] >>> local N2 = r(N) >>> local av2 = r(mean) >>> local sd2 = r(sd) >>> >>> ttesti `N1' `av1' `sd1' `N2' `av2' `sd2', unequal >>> >>> John >>> >>> John Luke Gallup >>> Department of Economics >>> Portland State University >>> >> > * * 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/