# [R] understanding the output

Ronaldo Reis Jr. chrysopa at insecta.ufv.br
Thu Jun 20 13:55:00 CEST 2002

```Hi all,
I try to understand the output of the summary(model).
I make a simple model.

> summary(m1anova)

Call:
glm(formula = peso ~ gen)

Deviance Residuals:
Min       1Q   Median       3Q      Max
-4.3114  -2.3788  -0.9167   2.1581   5.7856

Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept)   4.8660     0.9808   4.961 0.000101 ***
gen2g         3.8504     1.3870   2.776 0.012459 *
---
Signif. codes:  0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1

(Dispersion parameter for gaussian family taken to be 9.618818)

Null deviance: 247.27  on 19  degrees of freedom
Residual deviance: 173.14  on 18  degrees of freedom
AIC: 105.92

Number of Fisher Scoring iterations: 2

I need the mean and se to make an plotbar (I know to make a plotbar)
The mean is easy to get.

> tapply(peso,gen,mean)
1g     2g
4.8660 8.7164

The values is the same in estimate.
But the SE, when I try using tapply the SE is different os the SE of
estimates. look

> tapply(peso,gen,sd)/sqrt(tapply(peso,gen,length))
1g        2g
0.8665567 1.0829789

Why this difference? What SE I can use with mean???

When I use others errors that dont gaussian (poisson, binomial, etc), the mean
is easy transformed (exp(x) for poisson) but how to use the SE? I can to use
always the SE on the summary(model)? Or need transformation?

Thanks
Ronaldo

--
Hello, GORRY-O!!  I'm a GENIUS from HARVARD!!
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