I have two sets of experimental data for exponential decays of isotopes and I calculated the ratio of the two isotopes as a function of time. The theoretical model and the fit of the experimental data are respectively :
$1.04\text{e}^{-0.000856008t}$
$1.03154\text{e}^{-0.000457549t}$
The two curves are near of each other (I'm only interested in comparing the [0-110] x-range) but is there a way to calculate an error between the two curves (like a standard deviation)? I need to determine if the data are normally distributed so I thought getting the standard deviation from the theory/fit would be a correct way... Any ideas?