R help - Jun 2010 - Standard error of regression coefficient

Hi all,

This should be a very simple question for you, whereas it is proving devilish
for me.

How do I output the STANDARD ERROR of the regression coefficient (i.e., the
standard error of b) from a simple linear regression?

Consider this data, taken directly from ?lm:

ctl <- c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14)
trt <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69)
group <- gl(2,10,20, labels=c("Ctl","Trt"))
weight <- c(ctl, trt)

The problem is that neither of these lines of code seem to show me what I'm
looking for:
> lm(weight ~ group)
Call:
lm(formula = weight ~ group)

Coefficients:
(Intercept)     groupTrt  
      5.032       -0.371
> anova(lm.D9 <- lm(weight ~ group))
Analysis of Variance Table

Response: weight
          Df Sum Sq Mean Sq F value Pr(>F)
group      1 0.6882  0.6882  1.4191  0.249
Residuals 18 8.7292  0.4850

So what's the secret, then?

Thanks very much R users!
Josh



      
	[[alternative HTML version deleted]]

Josh B wrote:
> Hi all,
> 
> This should be a very simple question for you, whereas it is proving
devilish for me.
> 
> How do I output the STANDARD ERROR of the regression coefficient (i.e., the
standard error of b) from a simple linear regression?
> 
The first 'See Also' in ?lm is for ?summary.lm, which will give you what
you
want.  So simply pass your lm object to summary.