I was asked a question about the correlation coefficient. On calculators, this is the r-value that may pop up when you have done a regression. If this value is close to -1 or 1, the data points in question provide a good fit to the proposed equation. Actually, this r-value only applies to linear regressions, it is only defined there.

Someone said that that was not correct, seeing as the r-value also occurs on logistic or exponential regression. Actually, these are also linear regressions, they are transposed into linear relationships before regression analysis is carried out.

Anyway, now that calculators are too old, and Excel is too expensive, how do we carry out such a regression with the correlation coefficient also calculated? The answer (again) is GeoGebra. OK, to be fair, OpenOffice could probably just as well be used for this, but since I am a GeoGebra fan…

In the video below I enter some data points, do the regression and find the correlation coefficient. The menus are in Norwegian, but I am sure you can find the right commands in whatever language you want. You can easily change language in GeoGebra from the settings menu.

This entry was posted on Wednesday, January 26th, 2011 at 15:41 and is filed under GeoGebra, mathematics. You can follow any responses to this entry through the RSS 2.0 feed.
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2 Responses to Correlation coefficient on GeoGebra

Wow, I didn’t think anyone read this blog!🙂 As for your question I have to admit I don’t know. I don’t see why it wouldn’t work, it works in the present version of the chrome app, for instance. So my guess is “yes”, but I have been disappointed on some of the features of the pad-versions.

I don't know if I qualify as a researcher (actually, I know I don't), but at least I WORK as a researcher within higher education. I am a lecturer in mathematics in Norwegian teacher education. This blog will show some of the thoughts, software products, scientific tidbits and ramblings I encounter in this area of work. I hope you leave some comments in the... comments field.

Thank you, it was really helpful.

Do you know if the ipad version of geogebra can do this too?

Wow, I didn’t think anyone read this blog!🙂 As for your question I have to admit I don’t know. I don’t see why it wouldn’t work, it works in the present version of the chrome app, for instance. So my guess is “yes”, but I have been disappointed on some of the features of the pad-versions.