On 5 Feb 2002 08:28:05 -0800, [EMAIL PROTECTED] (Wuzzy) wrote: > Is it possible that multicollinearity can force a correlation that > does not exist? > > I have a very large sample of n=5,000 > and have found that > > disease= exposure + exposure + exposure + exposure R^2=0.45 > > where all 4 exposures are the exact same exposure in different units > like ug/dL or mg/dL or molar units.
Now, see, that is totally, thoroughly ignorant. You made a model with the "exact same exposure in different units", which is something that no one would do, who had understood even one single semester of intro-to-statistics. > > Nonetheless when I do a simple correlation (pearson) I found that the > exposure in ug/dL did not affect the disease. > I find it extremely likely that you do not know how to read the computer printout and then tell us what you have read. > This seems hard to believe as my sample is relatively large.. > I don't believe the 0.45 R^2 is possible but was shocked by it. I'll > try to rerun it in other, more realistic models. My advice is: Please ask for local help from someone who can lead you through analyses, step by step. If you insist on asking like this, I suggest that you cut-and-paste some computer output; or e-mail the full dataset to your eventual e-mail helper. -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =================================================================
