I'm using Fit and FindFit to get a best fit function that is some rate parameter "a" multiplied by the square root of x. I am wondering if there is some way to gauge how confident I am of a given fit-- some kind of Pvalue or standard error for the rate parameter or something? I know of ways to do this for a linear fit (linear regression analysis packages), but I don't know of any mathematica packages that could give me such information for a nonlinear fit. Is there something I have missed? Ultimately what I would like to do is find out if two fit functions are significantly different from oneanother.
Thanks for any help!