Sample Design Tables 2025-2026

Attachment 4

Sample Design Tables 2025-2026

Attachment 4: Sample Design Tables 2025-2026

Table 1 shows the overall sample design at each stage for a single year of data collection. The 2025 and 2026 samples are selected at the same time, but each year is nationally representative as the primary sampling units (PSUs) are randomly assigned to years within each stratum.

Table 1: Sample Design with Single-Year Sample Size for Each of Four Stages: NHANES 2025-2026

Stage 1 Area Cluster = Public Use Microdata Area (PUMA)		Stage 2 Segment = Census Block Group(s) (CBGs)
Frame	List of PUMAs available from U.S. Census Bureau data covering 50 states plus Washington, DC.	Frame	List of block groups within the PUMAs available from U.S. Census Bureau data covering 50 states plus Washington, DC. Small block groupsc are combined with neighbors to form SSUs.
Sample Size	20 PUMAs	Sample Size	12 SSUs per PSU (240 per year)
Selection Method	Probability proportional to composite measure of size (CMOS) summed over Secondary Sampling Units (SSUs).	Selection Method	Probability proportional to CMOS
Stratification	10 explicit strata constructed with CDC’s Social Vulnerability Indexa [5 levels] crossed with Urban/Rural proportion.b Implicit stratification (i.e., sorting) by region within 10 strata.	Stratification	No explicit strata; implicit stratification (sorting) by CBG number for geographic dispersion across the PSU.
Stage 3 Dwelling Units = Addresses		Stage 4 Persons Within Screened DUs
Frame	Address-based sample (ABS) frame for sampled (SSUs) supplemented with FE as needed	Frame	Roster of dwelling unit residents
Sample Size	10,753 dwelling units (DUs)	Sample Size	10,448 persons
	(average 538 per PSU, 45 per SSU)		(average 522 per PSU, 44 per SSU, 1.88 per DU)
Selection Method	Stratified simple random sampling	Selection Method	Stratified random sample
Stratification	ABS indicator for likely presence of a NH Black DU resident (Yes vs. No/Unknown) crossed with likely presence of children in the DU (Yes vs. No/Unk)	Stratification	Age group for rostered DU residents [3 levels]: 0-11 years, 18-64 years / unknown age, and 12-17 years or 65 years or older (combined)

Table 2 shows the summary distribution by age for the examination targets in 2025-2026; the targets are both by race/ethnicity and age groups along with the population estimates.

Table 2: Population Distribution, Expected Response Rate, Targeted Health Exam, and Estimated Sampling Rate per Year by Race/Ethnicity and by Age Group Domains: NHANES 2025-2026

Race/Ethnicitya	Age (Years) Group	Populationb		Annual Exam Target
		Count	Percentagec	Count	Percentagec
Hispanic	Total	61,956,276	18.9	1,175	23.5
Non-Hispanic Black		38,193,267	11.6	1,075	21.5
Non-Hispanic Other		227,801,186	69.5	2,750	55.0
Total	0–4	18,581,718	5.7	521	10.4
	5–11	28,439,237	8.7	680	13.6
	12–17	26,261,219	8.0	475	9.5
	18–44	117,259,097	35.8	1,435	28.7
	45–64	82,650,508	25.2	1,090	21.8
	65+	54,758,950	16.7	800	16.0
Total		327,950,729		5,000

^a NH Other includes persons identifying as more than one racial group.

^b Population counts from the American Community Survey 2021 1-year microdata, excluding military persons living in residential dwelling units and those persons living in institutional group quarters.

^c Unweighted percentage within the overall total.

Table 3 includes the expected sample size and response rate for each stage of selection expected in 2025.

Table 3: Annual Dwelling Unit Sample Size, Estimated Number of Interviewed and Examined Survey Participants, and Unweighted Response Rates: NHANES 2025

Characteristic	Count	Unweighted Percentage
Dwelling Units (DUs):
Initial Sample of DUs	10,753
Occupied DUs	9,140	85.0
Screened DUs	6.398	70.0
DUs with one or more Survey Participants (SPs)a	5,566	87.0
Survey Participants:
Count	10,448	-
Average Count per DU	1.88	-
Completed Survey Person Interviews	5,882	56.3
Completed SP Exams	5,000	47.9
Anticipated Unweighted Response Rate:
Screened DUs (among occupied)		70.0
Conditional SP Interview (among sampled)		56.3
Conditional Exam (among interviewed)		85.0
Overall SP Interview (= Screened × Conditional SP)		39.4
Overall Exam (= Overall SP × Conditional Exam)		33.5

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