Dear Ting-Wen,

This is a question about statistical philosophy in general, not specific to
tests for phylogenetic signal.  How best to correct for making multiple
tests with related data is a huge and complicated topic.  Another issue is
whether your traits are correlated with each other, which would affect
views on what would be best to do.  In any case, beware that
simple Bonferroni correction is probably overly conservative, so perhaps at
least try something like sequential Bonferroni correction, if you do
attempt correction.

(Aside from the points above, I am assuming that the 18 compounds do not
add up to 100% of the sample.  If they do, then you would only want to
analyze 17 of them.)

Ted Garland

On Sun, Dec 11, 2016 at 2:06 PM, Chen, Ting-Wen <> wrote:

> Dear all,
> I’m analysing some chemical compositions of species and considering them
> as “traits”, let’s say, 18 different compounds concentration in 37 species.
> I test phylogenetic signals in the percentage concentration of these
> compounds using Blomberg’s K and Pagel’s lambda using the function
> “phylosig". In Blomberg’s K I apply randomisation for the traits values on
> the tree to have a p-value for the corresponding trait and in Pagel’s
> lambda using likelihood test to get the p-value, resulting in several
> traits with phylogenetic signals as indicated by both K and lambda. Because
> phylogenetic signal is tested one by one, i.e. repeating 18 times for 18
> compounds. Would you suggest that I have to adjust the p-values using e.g.
> bonferroni corrections? I have some compounds with p-values for both K and
> lambda about 0.02 (e.g. compound “I", K=0.656, lambda=0.633), while some
> other about 0.002 (compound “R", K=0.849, lambda=0.817). Is it safe to
> conclude that compound “I” also has a phylogenetic signal?
> Any idea will be very appreciated. Thank you!
> All the best
> Ting-Wen
> --
> Ting-Wen Chen
> J.F. Blumenbach Institute of Zoology and Anthropology
> Georg August University Goettingen
> Berliner Str. 28
> D-37073 Goettingen, Germany
> Tel: +49-55139-10943
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