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HP 48gx scatterplot? - Printable Version

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HP 48gx scatterplot? - Karen Gibson - 05-16-2003

Any help with this question is greatly appreciated. I apologize now for my lack of knowledge on this calc. I've only had it a month, I've figured most of the things out on my own, but this one has me stumped.

I am doing a scatterplot, that part I have down. I need to get the equation for the data after I have plotted it. I've tried using the STATL button on the menu, then FCN VIEW to get the equation. For some reason it is returning an incorrect equation. I know this because I've tried several out of my Algebra book and do not get the correct answer. When I do the STATL instead of following the data plotted it does a diagonal line accross the screen and this is the equation it returns.
Can anyone help?
Thank you,
Karen


Re: HP 48gx scatterplot? - R Lion (Spain) - 05-16-2003

Hi Karen:
Could you mail me with the data and the answers (the correct and the incorrect ones)
More help about hp48 in http://groups.google.com/groups?as_ugroup=comp.sys.hp48

Raul


Re: HP 48gx scatterplot? - Karen Gibson - 05-17-2003

Hi Raul,
Here is the info:
x values: 0, 7, 14, 20, 24
y values: 26.2, 19.2, 16.6, 18.8, 19.5
Plot is stretched u shape opening upward.
Correct answer is: f(x) = .0402302792x^2 - 1.214631021x + 26.02596908
Answer on my HP: 23.2788829787 -.247606382979x

Thanks for the help.
Karen


Re: HP 48gx scatterplot? - R Lion (Spain) - 05-17-2003

You are getting the Linear regression but you want a polynomial regression. You need some extra software (i.e.: http://www.hpcalc.org/hp48/math/statistic/bfit.zip )
I have got your expected results with that.
Hope this helps.

Raul


Re: HP 48gx scatterplot? - Karen Gibson - 05-17-2003

Thanks Raul, I'll try that, need to get some more hardware first.