[R] A simple question about summary.glm
Uwe Ligges
ligges at statistik.uni-dortmund.de
Tue Jul 31 11:50:28 CEST 2007
michal33 wrote:
> Hello,
>
> I am new to R and have tried to search similar questions but could not find
> exactly what I am looking for, but I apologize if the question was already
> asked.
>
> I have 10 different treatments and want to know whether they affect the sex
> ratios of insect emergence. After running the glms I got this table:
>
> Df Deviance Resid. Df Resid. Dev F Pr(>F)
> NULL 133 9250.3
> sex 1 481.5 132 8768.9 7.7212 0.006314 **
> trt 9 1099.1 123 7669.7 1.9585 0.049780 *
>
> But now I would like to know WHICH of the treatments was significant. I
> tried to use Tukey test but for some reason it does not work.
> My question is:
> I used the following function:
>> summary(file.name, corr=F)
> and got the following table:
> Deviance Residuals:
> Min 1Q Median 3Q Max
> -14.118 -4.808 -1.466 2.033 33.882
> Coefficients:
> Estimate Std. Error t value Pr(>|t|)
> (Intercept) 8.696e+00 1.893e+00 4.594 1.06e-05 ***
> sexm -3.791e+00 1.364e+00 -2.779 0.00631 **
> trtccc -1.050e+00 4.325e+00 -0.243 0.80859
> trtcga3 2.450e+00 4.325e+00 0.566 0.57211
> trtcga4 -2.300e+00 4.325e+00 -0.532 0.59584
> trtg 1.550e+00 2.497e+00 0.621 0.53593
> trtga4 -5.550e+00 4.325e+00 -1.283 0.20183
> trtp 5.422e+00 2.566e+00 2.113 0.03658 *
> trtpg -1.850e+00 2.497e+00 -0.741 0.46019
> trtw -3.634e-17 2.497e+00 -1.46e-17 1.00000
> trtwg -3.750e+00 2.497e+00 -1.502 0.13573
>
> What do the stars mean?
Well, you omitted the last lines from the output which include:
Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
i.e. *** for values < 0.001; * for values in [0.01, 0.05) etc.
Uwe Ligges
Is it the same as Tukey test that tells me which
> treatment is different from which? i.e. is trtp (with *) significantly
> different to the control (which, by the way do not appear in this list and I
> do not know why)?
>
> Thanks
> Michal
>
>
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