Table 2.

Mean ± SD, mean difference, and effect sizes for free-running circadian period comparisons between sex and ancestry within and between age groups.

		Adolescents	Adults	Mean Age Difference
		24.19 ± 0.22 h	24.22 ± 0.24 h	1.8 mins (d=0.13)
Ancestry:
African American		24.15 ± 0.26 h	24.07 ± 0.25 h	4.8 mins (d=0.31)
Non-African American1		24.23 ± 0.19 h	24.30 ± 0.20 h	4.2 mins (d=0.36)
Mean Ancestry difference		4.8 mins (d=0.36)	13.8 mins* (d=1.05)
Sex:
Male		24.23 ± 0.22 h	24.26 ± 0.24 h	1.8 mins (d=0.13)
Female		24.16 ± 0.23 h	24.17 ± 0.24 h	0.6 mins (d=0.04)
Mean Sex difference		4.2 mins (d=0.31)	5.4 mins (d=0.37)

^*p < .01; Cohen’s d effect size: 0.2 = small; 0.5 = medium; 0.8 = large

¹White + Other ancestry categories (see Table 1).

Note: Age did not differ between African American and non-African American adolescents or adults. Age did not differ between male and female adolescents or adults.