Each plot shows the χ2 distribution (black curves) for the degrees of freedom associated with each comparison (8 degrees of freedom for EnHD, left; 5 degrees of freedom for RNase H, right). The vertical lines denote the χ2 value calculated for each force-field/software package combination (AMBER, red; GROMACS, green; ilmm, purple; NAMD, blue) as well as the expectation value for that distribution (black).