Re: [R] logistic regression

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Thu 16 Feb 2006 - 18:13:14 EST

On Thu, 16 Feb 2006, Chris Lawrence wrote:

> On 2/15/06, Taka Matzmoto <sell_mirage_ne@hotmail.com> wrote:
>> I have two bianry variables (X and Y) and one continuous variable (Z).
>>
>> I like to know, after controlling for the continuous variable, where one of
>> the binary is significantly related to the other binary variable using
>> logistic regression
>>
>> model <- glm(Y ~ X + Z, family=binomial)
>>
>> Is checking the significance of the coefficient of X a proper way for doing
>> that ?
>
> Yes, that will do it.

Sorry, not so. That is a Wald test, and its power goes to zero as the true effect increases. You need to do a likelihood ratio test via anova() to get a reasonable test.

Details in MASS (see the FAQ).

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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Received on Thu Feb 16 18:17:29 2006

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