[R] how to test whether two slopes are sign. different?

Harold Doran hdoran at nasdc.org
Mon Jul 21 14:15:13 CEST 2003

Dear Stoet

This can be handled well in using a mixed-effects model, library (nmle). You can use the lmList option to check whether the slopes differ across populations.

Harold C. Doran
Director of Research and Evaluation
New American Schools
675 N. Washington Street, Suite 220
Alexandria, Virginia 22314

-----Original Message-----
From: Gijsbert Stoet [mailto:stoet at volition.wustl.edu]
Sent: Sunday, July 20, 2003 10:51 PM
To: r-help at stat.math.ethz.ch
Subject: [R] how to test whether two slopes are sign. different?


  suppose I do want to test whether the slopes (e.g. determined with
lsfit) of two different population are significantly different, how do
I test this (in R). Say for example, I found out what the slope
between age and number of books read per year is for two different
populations of subjects (e.g. 25 man and 25 woman), say using
lsfit. How can I tell whether the slopes are different in R. (And how
would I do it for regression coefficients?)

Thanks a lot for your help.

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