
Am 14.09.2007 um 15:54 schrieb Petr PIKAL:

>> Petr PIKAL wrote:
>>> Hi
>>>
>>> r-help-bounces@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@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.
>>>
>> True, for that particular set of data. I did make that point in my  
>> first
>> reply (tried to, anyways), but I didn't repeat it the second time.
>>
>> If you look back, you'll see that Birgit was also doing
>>
>> TTest75<-t.test(Fem75, Mal75, alternative= "two.sided", paired= TRUE)
>>
>> and presumably there are several similar sets of data. This  
>> "works" in
> the
>> sense that it produces a test, but one could get the suspicion  
>> that it
> is only
>> using a small subset of available data if the dropout rate is
> approaching that
>> of Fem66/Mal66. Hence the discussion of the general case.
>
> I see, sorry I did not noticed before. But everything depends on which
> hypotheses she wants to test. She told us about 334 different plant

348

> species (male and female) and if she wants to test if male and  
> female is
> different

yes

> she does not have many other options.
>
> Petr
>
>>
>>> 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@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
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>> -- 
>>>>    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
>>>
>>>> ______________________________________________
>>>> R-help@r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> PLEASE do read the posting guide
>>>>
>>> http://www.R-project.org/posting-guide.html
>>>
>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>
>>>
>>> ______________________________________________
>>> R-help@r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>
>>
>> -- 
>>    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
>>
>> ______________________________________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting- 
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

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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