Model comparisons to test lower-level and interactive effects using Equations 13 or 14 are well known (cf. Cohen et al., 2003, pp. 308–316), so are not detailed here. But, Equations 11–14 are only as informative about the ordinal or disordinal nature of the interaction as was true of Equations 1 and 2. Modified versions of Equations 4 and 6 could be developed to estimate cross-over points for different groups, but SEs or CIs would still be unavailable for these estimates.
