[R] A simple question about summary.glm

[Uwe Ligges]

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
> 
>