Logarithmic Regression: Different correlation from 3 different calculators
06-09-2015, 07:45 PM (This post was last modified: 06-09-2015 07:53 PM by Dave Britten.)
Post: #3
 Dave Britten Senior Member Posts: 2,074 Joined: Dec 2013
RE: Logarithmic Regression: Different correlation from 3 different calculators
(06-09-2015 07:36 PM)CR Haeger Wrote:  I wonder if your r and r^2 values change slightly if you run the regression on normalized X, Y data?

Also, I think that calculating r for non linear regressions may require separate calculations of SSE and SST, then using r = sqrt(1 - SSE/SST) .

Yeah, I'm not enough of a statistician to know if there's a problem with my calculation method that's causing inaccuracy, or if I'm supposed to be using a different formula entirely. I know a lot of the HPs with accumulated stats just transform x and/or y on the fly as you enter them, so I'm not sure what else I'd have to do. I'll have to crack open my old stats 215 textbook later and see what it says about curve fitting.

EDIT: Running a linear regression on a list of transformed ln(x) values gives me the same value for r as doing logarithmic regression on the original x values, at least with the 36X Pro. So I assume the formula is the same, but something must be clobbering numeric accuracy along the way. Hmm...
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 Messages In This Thread Logarithmic Regression: Different correlation from 3 different calculators - Dave Britten - 06-09-2015, 03:09 PM RE: Logarithmic Regression: Different correlation from 3 different calculators - CR Haeger - 06-09-2015, 07:36 PM RE: Logarithmic Regression: Different correlation from 3 different calculators - Dave Britten - 06-09-2015 07:45 PM RE: Logarithmic Regression: Different correlation from 3 different calculators - CR Haeger - 06-09-2015, 08:51 PM RE: Logarithmic Regression: Different correlation from 3 different calculators - groundbeef - 06-09-2015, 09:37 PM RE: Logarithmic Regression: Different correlation from 3 different calculators - Dave Britten - 06-09-2015, 10:00 PM RE: Logarithmic Regression: Different correlation from 3 different calculators - Paul Dale - 06-09-2015, 10:38 PM RE: Logarithmic Regression: Different correlation from 3 different calculators - groundbeef - 06-09-2015, 10:53 PM RE: Logarithmic Regression: Different correlation from 3 different calculators - groundbeef - 06-09-2015, 11:16 PM RE: Logarithmic Regression: Different correlation from 3 different calculators - CR Haeger - 06-09-2015, 11:26 PM RE: Logarithmic Regression: Different correlation from 3 different calculators - Dave Britten - 06-10-2015, 12:12 AM RE: Logarithmic Regression: Different correlation from 3 different calculators - CR Haeger - 06-10-2015, 03:28 PM

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