The data is a list of measurements of power $P_i$ with estimated uncertainty $\Delta P_i$ and another list with measurements of positions $x_i$ and estimated uncertainties $\Delta x_i$. All the $\Delta x_i$ have the same value. It looks like a Gaussian distribution and I want to find its FWHM.
I have heard of the method of least squares. For this I just need fit function (Gaussian), the $P_i$, the $x_i$ and the $\Delta P_i$. The problem is that I do not know how to use the uncertainty in position with this method.