Comparison of the model coefficients (slope, α, and intercept, β) of the chemical trends between M dwarfs (orange dots) and GK dwarfs (green dots), along with the statistical test results. The dashedanddotted ellipses indicate the 1σ and 2σ contours of their best-fit values (the dots in brown and in darker green). Here, we show only the cases for C, O, Mg, and Si; the full set of comparisons of these model coefficients for all elemental pairs can be found in Fig. B.9. See text for details of the statistical test of the null hypothesis, $H_0:\overline{{(\alpha ,\beta )}_M}=\overline{{(\alpha ,\beta )}_{GK}}$.