Originally Posted by

**Ackbeet** Your numbers are fine for a linear fit to the logarithm data. However, the plot of the logarithm of the data looks a lot more like a quadratic than a straight line. That is, you can write

$\displaystyle \ln(\phi(x))=\ln(a_{1})+a_{2}x=5.7763-0.2924x,$ with an $\displaystyle R^{2}$ value of $\displaystyle 0.965.$ That's good, but not great. On the other hand, if you go with a quadratic fit to the logarithm data, that is, you assume

$\displaystyle \phi(x)=e^{ax^{2}+bx+c},$ then

$\displaystyle \ln(\phi(x))=ax^{2}+bx+c=0.0198 x^{2}-0.4905x+6.0734,$ with an $\displaystyle R^{2}$ value of $\displaystyle 0.9995,$ which is an incredibly good fit.

Just a thought.