[R] In fact this is a Stats question, but...

[eesteves at ualg.pt]

Dear All,
I'me having (much) trouble understanding why it happened and answering  
a referee's comment to part of a submitted manuscript. I've tried to  
google for help but... I'm really confident that although this is a  
R-Help list someone can help me!

I used R to do an ANCOVA w/ RNA/DNA as the dep var, sl as the indep  
var and gut (a factor w/ levels: prey and empty) as the covariate:

> RNADNA.sl.gut<-lm(sqrt(RNADNA)~gut*sl,subset=gut!="Yolk-sac",data=cond)
> summary(RNADNA.sl.gut)

The results from this are:

(...)
Coefficients:
              Estimate Std. Error t value Pr(>|t|)
(Intercept)  0.856266   0.052252  16.387  < 2e-16 ***
gutPrey     -0.009568   0.092170  -0.104    0.917
sl           0.030575   0.004648   6.578 6.35e-11 ***
gutPrey:sl   0.002285   0.007313   0.313    0.755
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Residual standard error: 0.3312 on 1692 degrees of freedom
Multiple R-Squared: 0.05847,    Adjusted R-squared: 0.0568
F-statistic: 35.02 on 3 and 1692 DF,  p-value: < 2.2e-16

(...)

The question raised by referee is related to the "incompatibility" of  
the low r2 (0.057) and the high significance (p<<0.0001) of the model.  
I've interpreted/used this result in the following way: although  
there's a significant relationship between RNA/DNA and sl, it's very  
weak; besides, no gut effect on the relationship as been found!

Sorry for the off-topic question but...

Sincerely, Eduardo Esteves