
Am 14.09.2007 um 12:05 schrieb Peter Dalgaard:

> S Ellison wrote:
>>
>>>>> Peter Dalgaard <P.Dalgaard@biostat.ku.dk> 14/09/2007 09:26:16 >>>
>>>>>
>>>> So what can I do now to solve my problem?
>>>>
>>>> Do you think I should not use paired=TRUE?
>>>>
>>> You *can* only use it when you have pairs, and you must do it  
>>> then, to
>>> correct for intra-pair correlation. The drawback is that it looks  
>>> only
>>> at complete pairs, throwing away all the singlets. It is possible to
>>> recover the information from the singlets , basically by combining a
>>> paired test for the pairs and an unpaired one for the singlets.  
>>> (Someone
>>> must have written this down, but I'm afraid I don't have a nice  
>>> reference).
>>>
>>
>> Question: Could you achieve this kind of outcome with lme? stack  
>> the two groups, mark the observations y by subject (ie the pair  
>> ID) and group (treatment, presumably), and do something like
>>
>> anova(lme(y~group, data=d, random=~1|subj, na.action=na.omit))
>>
>> Or is that just disguising one of those nasty unbalanced 2-way  
>> anova problems?
>>
> 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?

			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@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@systbot.uzh.ch






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