On Sep 13, 2011, at 9:43 AM, RCulloch wrote:
Dear John,
Thank you for that, and for explaining why the abline() command wont/
dosen't
work. The approach is based on reviewers comments that I am a tad
sceptical
about myself but yet curious enough to test their suggestion......I
don't
think it is very straightforward to explain; however, it involves
using the
residuals of the lm() and plotting them against a covariate to assess
whether or not the deviation from the 1:1 relationship is in someway
influenced by the other covariate. I hope that shines a small amount
of
light on this rather unorthodox approach?!
Plotting the residuals against a covariate is a standard way to assess
the assumption that the residuals are distributed normally around each
continuous regressor and have no non-linear relationship around each
continuous regressor. It is not to assess a "1:1 relationship",
whatever that is. I think we would need to see a complete quotation
of the reviewer's comments before deciding who is confused in this
interchange.
--
David Winsemius, MD
West Hartford, CT
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