# Re: [R] clarification about glm

From: Daniel Malter <daniel_at_umd.edu>
Date: Sat, 23 Feb 2008 15:34:43 -0500

Hi Sigalit,

yes, you can see this from the fact that the table says unit"1" meaning that it compares 1 to 0 and not vice versa. Everytime you regress on dummies the label will have added this to the original variable name. Say you have gender "male" and "female". Then "gendermale" in the label of your summary table would indicate that "female" is coded 0 and male 1 and that you therefore compare how much more or less of the dependent variable males "have" over females (and not vice versa). In case of a binomial regression it would of course be how much more or less likely they are on average (with the appropriate transformation) ...

Cheers,
Daniel

cuncta stricte discussurus

-----Ursprüngliche Nachricht-----
Von: r-help-bounces_at_r-project.org [mailto:r-help-bounces_at_r-project.org] Im Auftrag von sigalit mangut-leiba
Gesendet: Saturday, February 23, 2008 3:05 PM An: r-help

Hello,
I have a question about glm:
if i have a binary covariate (unit=1,0)
the reference group would be 0? (prediction for unit=1)

example:

dat1<-data.frame(y,unit,x1,x2)

log_u <- glm(y~.,family=binomial,data=dat1)

summary(log_u)

Estimate Std. Error z value Pr(>|z|)

```(Intercept) -0.54247    0.24658  -2.200   0.0278 *
unit1       -0.13052    0.22861  -0.571   0.5680
aps          0.03098    0.01433   2.162   0.0306 *
tiss0        0.02522    0.01101   2.291   0.0219 *

```

Thank you,

Sigalit.

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