National Health and Nutrition Examination Survey

Why I was selected

If selected for this survey, your participation is important.


How was I selected?

Selection Stages diagram

Stage 1 All the counties in the United States are divided into 15 groups based on their characteristics. One county is selected from each large group, and together they form the 15 counties in the NHANES surveys for each year.
Stage 2 Within each county, smaller groups (with a large number of households in each group) are formed, and between 20 and 24 of these small groups are selected.
Stage 3 All of the houses or apartments within those selected small groups are identified, and a sample of about 30 households are selected within each group.
Stage 4a NHANES interviewers go to each selected household and ask for information (age, race, and gender) on all persons in the household.
Stage 4b A computer algorithm randomly selects some, all, or none of the household members.

First, we find out if you’re eligible. The NHANES interviewer will come to your home and ask you a few questions about you and the other members of your household. NHANES interviewers always have identification with them that they will show you immediately. Once you answer a few questions, the interviewer will let you know if you are needed to participate further.

Page last reviewed: October 19, 2018