posted and e-mailed. On 24 Sep 2003 14:49:14 -0700, [EMAIL PROTECTED] (kjetil brinchmann halvorsen) wrote:
> On 24 Sep 2003 at 16:23, Rich Ulrich wrote: > [ snip, some] RU > > > > On (1). What sort of 'nonlinear' ? > > Engineers and psychologists often include simple polynomials > > when they say 'nonlinear', since these can draw curved lines; > > whereas statisticians are concerned with nonlinear-in-the- > > coefficients, which are more complicated. > > > > So, do you mean the easy nonlinear, or the tough one? KB > > That was the state some time ago non-linear -in-coefficients models > are not more any more difficult than linear models, there is a lot of > high-quality optimization software around now! If your statistics > package continues to make it difficult, or you does'n need it, or you > change package. It is time to start to use the more natural > terminology you say engeeneers and psychologists use. Some well-known > statisticians have also said so publically, like Jim Lindsey, which > uses the terminology that way in his books and on-line documents. > Algorithmic difficulties should not determine terminology any more. I found that idea interesting, the idea that what I called "[tough] non-linear is no longer more difficult than linear." But I think that the essential differences, unfortunately, extent far beyond the ease of using a stat-package. Yes, linear models *might* have gross difficulties about non-homogenous errors, and thus give you R-squared that is impossible to use. And tests that are unreliable. But the linear model, very often, is close-enough-to- correct that all those things are usable. But the appropriateness is *always* something to beware of, for nonlinear, unless you are following a well-worn path of precedent in your own area, where you can cite the authorities for using your choice of setting up the parameters. -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html "Taxes are the price we pay for civilization." . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
