[R] t.test() with missing values

[Petr PIKAL]

Hi

r-help-bounces at r-project.org napsal dne 14.09.2007 13:50:58:

> Birgit Lemcke wrote:
> >
> > Am 14.09.2007 um 12:05 schrieb Peter Dalgaard:
> >
> >> S Ellison wrote:
> >>>
> >>>>>> Peter Dalgaard <P.Dalgaard at biostat.ku.dk> 14/09/2007 09:26:16 >>>
> >>>>>>


<snip>


> >>>
> >> Yes, but....
> >>
> >> I don't think lme() will do better than what you can do by hand: Get 
two
> >> independent estimates of mu1-mu2 (one estimate from the pairs and one
> >> from the singlets), compute a weighted average using the s.e.'s and 
test
> >> that against zero (possibly after testing them for equality for good
> >> measure). This is easy if you use a plug-in approach: first assume 
that
> >> the s.e. are known, then plug in their empirical value. The tricky 
bit
> >> is to calculate the DF in the style of Welch's test.
> >
> >             I apologise but I really can not follow your explanations.
> > I am  R and Stastistics Beginner.
> >
> >             What do you mean with mu1-mu2 and what are s.e.´s?
> >
> That was a reply to S. Ellison. If you don't understand it, don't worry;
> you'll probably need to read a book chapter or more about weighted
> analyses to get up to speed for that. 
> 
> mu1, mu2 : (theoretical) mean for group 1, 2
> s.e.: standard error

But as Birgit actually does not have any paired values, according to the 
data she had sent, she can not do paired t.test at all. The only way is to 
compare averages from each vector by non paired t.test or to get some new 
values for which she have counterparts. 

Regards
Petr



> >             Once again thank you for your help.
> >
> >             Birgit
> >
> > 
> >
> > 
> >>
> >> --   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, 
Entr.B
> >>   c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
> >>  (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45)
> >> 35327918
> >> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45)
> >> 35327907
> >>
> >>
> >
> > Birgit Lemcke
> > Institut für Systematische Botanik
> > Zollikerstrasse 107
> > CH-8008 Zürich
> > Switzerland
> > Ph: +41 (0)44 634 8351
> > birgit.lemcke at systbot.uzh.ch
> >
> >
> >
> >
> >
> >
> 
> 
> -- 
>    O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
>   c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
>  (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 
35327918
> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 
35327907
> 
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