# Greater precision with regression?

I used my TI-83 to find the quadratic regression of two data columns. The accuracy wasn't close at all. So I tried cubic and then finally quartic regression. The accuracy still isn't close enough. Is there any way I can improve the accuracy? I can't add any more data, unfortunetly.

Edit 1:

To address Henry's comment, my plotted data looks similar to y=x^(1/3)

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It is difficult to comment without seeing the data. You could try plotting the points to see what the pattern looks like and whether that suggests anything. – Henry May 20 '11 at 22:54
If it is in fact a cube root, that explains why polynomials don't fit well. The cube root gets too flat for a polynomial. As I suggested below, taking the logarithm of all the data will check this. y=x^(1/3) implies log(y)=(log(x))/3 and you should get a good linear fit. – Ross Millikan May 20 '11 at 23:43

Take the logarithm of the data. If the data fits $y=exp(ax)$ your polynomial fitters will not do well, because polynomials can't increase that fast. But then $\log y=ax$ will be linear. – Ross Millikan May 20 '11 at 23:01
If, as you say, it looks like $y=x^\frac{1}{3}$, then you might try a power regression, which will give you a formula of the form $y=ax^b$.