I'm having trouble determining with confidence the deg.s of freedom (df) of a data set I'm dealing with. I'm dealing with a data set of around 40 observations. 4 sets of 10 observations measure at different temperatures from zero to T (of some interval delta), each set representing a different magnetic field B, giving as an output a value sigma, such that theoretically it should be described by a function sigma(T,B) (the null hypothesis). Since these observations are all distinct, I am guessing the df = 1, right? Also, I am aware the reduced chi^2 (r-chi^2) value is (chi^2)/df, and that a r-chi^2 value >> 1 or << 1 is bad. What r-chi^2 value is considered a "good" value when comparing experimental data to theoretical models (specifically in phyiscs)? Is there a specific academic source that confirms or supports this value?