Figure 4.

Regression functions for male (dotted black line) and female subjects (solid gray line).

$$\text{Male regression equation}:{\widehat{Y}}_{\mathit{\text{ij}}}=.04682-{.00442}^{*}{\mathit{\text{Span}}}_{\mathit{\text{ij}}}+.00059{\mathit{\text{Span}}}_{\mathit{\text{ij}}}^2$$

$$\text{Female regression equation}:{\widehat{Y}}_{\mathit{\text{ij}}}=.04583-{.00396}^{*}{\mathit{\text{Span}}}_{\mathit{\text{ij}}}+.00054{\mathit{\text{Span}}}_{\mathit{\text{ij}}}^2$$