National Health and Nutrition Examination Survey

Why Was I Selected?

This is an invitation-only opportunity to participate in NHANES.

You may be wondering how you were chosen.

You live in one of just 15 areas that NHANES will visit this year. We cannot go to every house in the U.S. so we randomly choose which ones to talk with. Your house­hold is one of a few selected in your commu­nity, and no one else can take your place.

You were randomly selected through a statistical process using U.S. Census information. As a selected participant, you represent up to 65,000 people like you.

Each step of our process is described below.

Image of vegetables and stethoscope
Image of sampling from largest geographical area to individuals.
Stage 1 All the counties in the United States are divided into 15 groups based on their characteristics. One is selected from each group and together they form the 15 counties in the NHANES survey for the year.
Stage 2 Within each of the 15 NHANES counties, smaller groups (such as neighborhoods) are formed, and between 20 and 24 of these small groups are selected.
Stage 3 All the houses or apartments within those selected small groups are identified, and a sample of about 30 households are chosen within each group.
Stage 4a NHANES will contact the selected household and ask a short set of questions (age, race, and gender) about everyone in the household.
Stage 4b A computer process randomly selects some, all, or none of the household members.

Be part of the 240,000 people who have already participated and have improved the health of everyone in the United States. Please participate!

Contact NHANES

If you have questions about NHANES, please call 1-800-232-4636.

For more information on NHANES visit the National Health and Nutrition Examination Survey homepage.