[R] Coefficients, OR and 95% CL
Frank E Harrell Jr
f.harrell at vanderbilt.edu
Tue Sep 23 14:37:02 CEST 2008
Eik Vettorazzi wrote:
> you will get odds-ratios by exponentiating the coefficients of this
> model, so
> will do this job. You may notice that this will produce an "OR" for the
> intercept part as well - which is not interpretable.
> For the confidence intervals for this odds ratio you have to
> exponentiate the borders of the "standard" confidence intervals for the
The approach of anti-logging a coefficient only works in the simple case
in which the variable is binary (or a one-unit change is of interest and
the variable is linear), doesn't interact with another variable, and the
reference cell desired equals the reference cell coded.
> Luciano La Sala schrieb:
>> Dear R-users,
>> After running a logistic regression, I need to calculate OR by
>> exponentiating the coefficient, and then I need the 95% CL for the OR
>> as well. For the following example (taken from P. Dalaagard's book),
>> what would be the most straightforward method of getting what I need?
>> Could anyone enlight me please?
>> Thank you!
>> glm(formula = menarche ~ age, family = binomial)
>> Deviance Residuals: Min 1Q Median 3Q Max
>> -4.68654 -0.13049 -0.01067 0.09608 2.35254
>> Estimate Std. Error z value Pr(>|z|) (Intercept)
>> -17.9175 1.7074 -10.49 <2e-16 ***
>> age 1.3549 0.1296 10.45 <2e-16 ***
>> Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
>> (Dispersion parameter for binomial family taken to be 1)
>> Null deviance: 974.31 on 703 degrees of freedom
>> Residual deviance: 223.95 on 702 degrees of freedom
>> (635 observations deleted due to missingness)
>> AIC: 227.95
>> Number of Fisher Scoring iterations: 9
>> R-help at r-project.org mailing list
>> PLEASE do read the posting guide
>> and provide commented, minimal, self-contained, reproducible code.
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
More information about the R-help