Table 5.

Percentage of Variability in Lung Function in the Third National Health and Nutrition Examination Survey (1988–1994) Explained by Age and Height, Race/Ethnicity, and Interaction Terms for Race/Ethnicity

Variable	Men				Women
	df	Regression Sum of Squares	Total Sum of Squares	% of Variability Explained by Variable	df	Regression Sum of Squares	Total Sum of Squares	% of Variability Explained by Variable
FEV1
Age and height	3	417,470,981	862,406,448	48	3	569,411,839	1,048,891,848	54
Race/ethnicity	2	105,279,869	862,406,448	12	2	110,732,577	1,048,891,848	11
Interaction by race/ethnicitya	6	4,596,765	862,406,448	0.53	6	861,943	1,048,891,848	0.08
FVC
Age and height	3	444,690,627	1,113,558,707	40	3	555,060,439	1,270,794,743	44
Race/ethnicity	2	197,778,933	1,113,558,707	18	2	188,336,757	1,270,794,743	15
Interaction by race/ethnicitya	6	6,288,087	1,113,558,707	0.56	6	1,346,520	1,270,794,743	0.11
FEV6
Age and height	3	508	1,139	45	3	625	1,311	48
Race/ethnicity	2	187	1,139	16	2	184	1,311	14
Interaction by race/ethnicity	6	7.307	1,139	0.64	6	0.9104	1,311	0.07
FEV1/FVC ratio
Age and height	4	74,192	246,600	30	4	74,192	246,600	30
Race/ethnicity	2	1,856	246,600	0.75	2	1,856	246,600	0.75
Interaction by race/ethnicitya	8	558	246,600	0.23	8	558	246,600	0.23

Abbreviations: FEV₁, forced expiratory volume in 1 second; FEV₆, forced expiratory volume in 6 seconds; FVC, forced vital capacity.

^aA significant interaction by race/ethnicity implies differences in the relation of age and height to lung function by race/ethnicity and, if high, would suggest the need for race/ethnic-specific equations.