Figure 3. Simple main effects computed by SPM. Panel A – boys’ comparison by tier. Panel B – girls’ comparison by tier. Panel C – tier comparison by sex. Tier #1 – best performers; Tier #2 – intermediate performers; Tier #3 – worst performers. SPM {t} – t-test for a simple main effect. p – significance value. Grey area denotes significant differences (p < 0.05) within the speed-time curve. Dash lines represent the 95% confidence intervals (95CI).