Re: st: Interpting Dichotomous

[Richard Williams <Richard.A.Williams.5@nd.edu>]

At 02:45 PM 8/22/2004 -0700, Syed O Masood wrote:
> In regression analysis, how do we interpret dichotomus
> variables...How would I know if it is male or female which accounts
> for decrease in blood flow.
It is not an either/or question.  The coefficient for a dummy variable 
shows you the status of one group relative to the other.  In your case, one 
gender scores 1.67 points lower than the other (or, if you prefer, one 
gender scores 1.67 points higher than the other).  Which one is 
higher/lower depends on how gender is coded.

To put it another way, it wouldn't make any sense to talk about an effect 
of gender if your sample only had one gender.  If males have higher scores 
it automatically follows that females have lower scores.  You don't say 
that one gender has an effect on blood flow while the other does not.

For brief discussions of dummy variables, see pp. 10-12 of

http://www.nd.edu/~rwilliam/stats2/l02.pdf

Or (see especially pp. 8-9)

http://www.nd.edu/~rwilliam/stats2/l51.pdf


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Richard Williams, Notre Dame Dept of Sociology
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