T. Florian Jaeger wrote: > > On 9/3/07, *Andy Fugard* <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> > wrote: > > [...] Faraway (2006, p. 13) mentions in passing > that "We would normally avoid using the t-tests for the levels of > qualitative predictors with more than two levels." His example is for > Gaussian multiple regression; perhaps that's important? > > that is because the levels of a qualitative predictor are often > collinear. collinearity is bad for tests that use the standard error > estimate of the coefficient. so, those issues should go away after you > center your predictors and go through other measures to remove/reduce > collinearity in your model.
Aha! Is there a standard reference for this? Many thanks, Andy -- Andy Fugard, Postgraduate Research Student Psychology (Room F15), The University of Edinburgh, 7 George Square, Edinburgh EH8 9JZ, UK Mobile: +44 (0)78 123 87190 http://www.possibly.me.uk _______________________________________________ R-lang mailing list [email protected] https://ling.ucsd.edu/mailman/listinfo.cgi/r-lang
