interpreting adonis results
On Wed, 2011-11-16 at 03:43 +0100, Gian Maria Niccol? Benucci wrote:
Hi all, I had 84 samples collected in 7 different sites. In each sample were individuated the different fungal species and recorded. I would test if exist a real difference between the sites and if exist a sort of site effect that structure the fungal communities... Then, I did adonis test
adonis(community.sq ~ location, data=env.table, permutations=999)
Call:
adonis(formula = community.sq ~ location, data = env.table, permutations =
999)
Df SumsOfSqs MeanSqs F.Model R2 Pr(>F)
location 6 12.593 2.09886 6.8867 0.34922 0.001 ***
Residuals 77 23.467 0.30477 0.65078
Total 83 36.060 1.00000
---
Signif. codes: 0 *** 0.001 ** 0.01 * 0.05 . 0.1 1
The significance is R2=0.349 at P=0.001
Can I assure that exist a strong site effect in structuring the communities
in each site?
Depends. The test is one of no effect of `location`. You have found evidence against this hypothesis and thus could reject this hypothesis, instead accepting the alternative hypothesis that there is an effect of `location`. As to the strength of this effect? ~35% of the sums of squares can be explained by `location`. Substantially more of the variance remains unexplained. As I know nothing about your subject area, I am unable to comment further on the strength of the relationship. Seeing as many ecologists whose work I read would say an effect is significant if the p-value was >= 0.05. Not that I subscribe to this way or working, but by that criterion, you have identified a significant `location` effect. HTH G
Thanks for helping, G. [[alternative HTML version deleted]]
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