How You Were Selected

Key points

  • The National Health and Nutrition Examination Survey uses a scientific process and U.S. Census information to select participants.
  • The four-stage process chooses several areas we visit each year.
  • In the last stage, scientific methods identify people like you who we ask to complete our interviews, health exam, and laboratory tests.
Illustration of diverse group of people

No one can take your place!

When an NHANES representative comes to your door, you may wonder how you were chosen.

You live in one of the areas that NHANES will visit this year. Your area was randomly selected using a scientific process and U.S. Census information.

NHANES staff won't be able to visit every house in the United States or even every house in selected areas. Instead, we randomly choose which households we visit. Your house­hold is one of a few selected in your commu­nity. We need you to help accurately represent thousands of people across the country just like you.

How we choose participants

Stage 1: Areas

Outline of the United States filled with photos of different people's faces.
NHANES divides the United States into areas based on how similar they are to each other. NHANES visits each of these areas every year.

Stage 2: Neighborhoods

Circle filled with a view looking down on a neighborhood street map
Within each area, NHANES selects neighborhoods where people live.

Stage 3: Households

Overhead depiction of a yellow house with white picket fence
Using a list of houses, apartments, condos, and other households in the selected neighborhoods, NHANES randomly chooses a small number for the survey.

Stage 4: People

laptop computer with outlines of people on the screen. Down arrow points from computer to 5 selected people
NHANES contacts every selected household to ask a short set of questions about people living there. Our computer program determines who in the household is eligible to participate in NHANES.


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