Table 1.

Descriptive Statistics for National Health and Nutrition Examination Survey (NHANES), National Health Interview Survey (NHIS), and U.S. Natality Samples With Mean Values and Standard Deviations for Variables.

Prediction	1a	1a	1b	1c	2
Data set	NHANES III	NHANES III	NHIS	NHANES I	U.S. Natality
Years	1988–1994	1988–1994	1990	1971–75	2013
Age range	16–29	16–49	18–49	18–54	12–50
Sample N	895	4,837	22,617	2,074	1,077,439
Age	20.2 ± 3.7	31.1 ± 9.4	33.0 ± 8.7	39.3 ± 9.1	25.6 ± 5.6
Body mass index (BMI), measured	24.2 ± 5.8	26.9 ± 6.8		23.68 ± 5.64
BMI, self-report	23.6 ± 4.9	26.0 ± 6.2	22.01 ± 4.74		26.37 ± 6.39
Low BMI since 18				20.25 ± 3.09
Waist/staturea	0.486 ± 0.083	0.542 ± 0.098
Waist–hip ratioa	0.806 ± 0.066	0.851 ± 0.076
Bed disability days			5.4 ± 21.7
Major disability			2.7 ± 16.2%
Limited activity	6.27%	8.72%
Hospital days	0.08 ± 0.52	0.22 ± 0.70
Medical visits	3.13 ± 5.85	4.03 ± 6.80
Hypertension					6.00%
Operative delivery					29.34%

^a Waist measured 1 cm above iliac crest.