Scatterplot of LCD versus SCE for all cases, and for groups and subgroups split by lamina position and modulus. (
A)
Top left panel: Includes all cases and is equivalent to
Figure 3. Grouping by one factor, either lamina modulus (
B and
C) or position (
D and
G), produces groups with statistically significant associations between LCD and SCE. Grouping by modulus produces one strong (
B) and one weak (
C) association, both in the direction expected from the conceptual framework above (
Fig. 1). Grouping by lamina position results in something surprising: one relatively strong and significant relationship in the expected direction (
D) and one mixed (
G). The group with the mixed result was interesting because the association between LCD and SCE was significant in the direction opposite to the theory in the parametric analysis and not significant in the nonparametric one. More refined splitting of the cases into subgroups by lamina modulus and position revealed the effects of the strong interaction between the two factors. Three subgroups (
E,
F, and
H) show clear, strong, and significant (in both analyses) LCD versus SCE relationships in the expected direction. However, the relationship was not significant in either analysis in the subgroup of deep and soft LCs. In addition, this figure also clearly shows some effects of the interaction between lamina modulus and position. For example, the effect of a change in lamina modulus is smaller in deep laminas (
E versus
F) than in shallow laminas (
H versus
I). Conversely, the effect of lamina depth is smaller in stiff laminas (
E versus
H) than that in soft laminas (
F versus
I). Each panel is labeled with the Pearson's product moment correlation coefficient (ρ) and Kendall's rank correlation (τ), colored
blue if statistically significant (
P < 0.01) or
gray if not.