Table 3.

Difference between Blacks and Whites in free-running period length (τ)

	Hours	Minutes
All Black (N=20) vs. All White (N=55)	.19	11.4
Black Women (N=17) vs. White Women (N=23)	.23	13.8

NOTE: τ was determined by the phase shift of the DLMO from before to after 3 days of free-running through an ultradian LD cycle. Here the term Black is equivalent to non-Hispanic Black or non-Hispanic African-American, and White is equivalent to non-Hispanic White or non-Hispanic Caucasian-American.