[R-sig-eco] power analysis

[ONKELINX, Thierry]

Dear Bridget,

It is not easy to deduct a formula for the power for the more
complicated models like linear mixed models. So what you can do in such
a case is to use simulations. Simulate your data under know conditions,
fit the model and see if you get a significant result. Repeat this a
large number of times for each condition and you get an estimate of the
power.

HTH,

Thierry 


------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
Thierry.Onkelinx at inbo.be
www.inbo.be

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of
data.
~ John Tukey

-----Oorspronkelijk bericht-----
Van: r-sig-ecology-bounces at r-project.org
[mailto:r-sig-ecology-bounces at r-project.org] Namens Bridget ONeill
Verzonden: vrijdag 26 juni 2009 19:03
Aan: R-sig-ecology at r-project.org
Onderwerp: [R-sig-eco] power analysis


I am trying to do power analyses for a linear mixed model and a
Kaplan-Meier survival analysis.  All of my searches have only turned up
the basic pwr commands, does anyone know what I should be using?

cheers, Bridget

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