Table 1. The effect sizes (Cohen’s d statistic) for intra-class comparisons in males and females. Age Classification 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 Male 1.4 .3 .9 .1 .8 .4 1.3 1.3 1.8 1.0 Female 2.0 .3 .1 .2 .9 .9 1.2 1.1 1.3 N/A Large effect size ≥ 0.80, medium effect size ≥ 0.50, small effect size ≥ 0.20. There was insufficient data in the female 65-69 age class preventing analysis. N/A indicates that insufficient data were available.