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Re: Reduced chi-square goodness-of-fit statistic [message #65064 is a reply to message #65050]

Sun, 08 February 2009 16:45

pgrigis
Messages: 436
Registered: September 2007

Senior Member

the reduced chi square is one if the error are accurate representation
of the errors in your data (with some assumption about their
distribution).
If you get chi-square much less than one, that means that you have
overestimated your errors.

Ciao,
Paolo

giorgosioanno...@gmail.com wrote:
> I got confused with the reduced chi-square goodness-of-fit statistic
> returned by the curvefit. Can anyone tell me what exactly this is? I
> had the impression that the fit is good when its value is near 1.
> However when I try to test it with some good fits I get really small
> values so I am not sure that what I thought is correct. For which
> values to we reject the good-fit hypothesis?
>
> In particular some of the data I have give me the following chi-
> square goodness-of-fit statistics after fitting them to a curve:
>
> chisq= 0.00018011358
> chisq= 0.00013042104
> chisq= 5.8597835e-005
>
> Are these good fits?
>
> And also what exactly is the unreduced chi-square goodness-of-fit
> statistic returned by the poly_fit and when do we reject the good-fit
> hypothesis there?
>
> Thanks,
> Giorgos

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[Message index]

		Re: Reduced chi-square goodness-of-fit statistic By: David Fanning on Mon, 09 February 2009 18:31
		Re: Reduced chi-square goodness-of-fit statistic By: pgrigis on Mon, 09 February 2009 14:35
		Re: Reduced chi-square goodness-of-fit statistic By: lbusett@yahoo.it on Mon, 09 February 2009 09:06
		Re: Reduced chi-square goodness-of-fit statistic By: giorgosioannou84 on Mon, 09 February 2009 07:59
		Re: Reduced chi-square goodness-of-fit statistic By: pgrigis on Sun, 08 February 2009 16:45

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