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Re: regress [message #65810 is a reply to message #65671]

Wed, 18 March 2009 04:26

jameskuyper
Messages: 79
Registered: October 2007

Member

anniebryant@gmail.com wrote:
...
> I am trying to do a basic linear regression. My variables are
> variance of ground-cover and variance of topography. All I want to
> determine is if topographic variance is a good predictor of ground-
> cover variance, i.e. does a high topo variance value do a good job of
> predicting a high ground-cover variance value? You don't think
> REGRESS is the way to go?

Step one should be to plot your two variables against each other. If
you've got two many data points, you might need to look at a 2-D
histogram, instead. Only use REGRESS if it seems plausible from such a
plot that there is a linear relationship between them. If it looks like
there's some other relationship between them, then you should fit to a
curve that more closely resembles that relationship.

However, if the two variables are only loosely connected, which is what
I'd expect in this case, no curve is going to be a particularly good
fit, and using a fitting routine is not the right way to approach this.
What you should be calculating is the correlation between the two variables.

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[Message index]

		regress By: anniebryant@gmail.com on Tue, 17 March 2009 14:45
		Re: regress By: Jeremy Bailin on Thu, 19 March 2009 07:37
		Re: regress By: Brian Larsen on Wed, 18 March 2009 06:07
		Re: regress By: jameskuyper on Wed, 18 March 2009 04:26
		Re: regress By: David Fanning on Tue, 17 March 2009 18:03
		Re: regress By: Jeremy Bailin on Tue, 17 March 2009 16:47
		Re: regress By: anniebryant@gmail.com on Tue, 17 March 2009 16:36
		Re: regress By: David Fanning on Tue, 17 March 2009 15:48
		Re: regress By: anniebryant@gmail.com on Tue, 17 March 2009 15:02
		Re: regress By: David Fanning on Tue, 17 March 2009 14:51
		Re: regress By: David Fanning on Tue, 17 March 2009 14:50

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