# Minimum chi squared estimation

1. Nov 24, 2011

### indie452

hi
i have some data (star counts) and i have a model and i want to perform min chi squared

so if i call my data di, and my model mi with std dev = $\sigma$i = 1

then $\chi^2 = \sum \frac{(di - mi)^2}{\sigma i^2}$

no my model is this mi = bi - Fo where bi is the background which has been assumed to be 5, and Fo is some constant flux. from this i am thus assuming that the data is ecpected to be a flat line.

Now i want to determine the min ch squared estimate for Fo, but i am not sure how.
I have gotten this far:
$\frac{d\chi ^2}{dFo} = -2\sum \frac{(di - bi - Fo)}{\sigma i^2}$ = 0

any help is appreciated thanks