A sample weight value is a measure of the number of people in the population represented by a specific sample person in NHANES. Sample weights are constructed for each two-year survey cycle to account for over-sampling, survey non-response, and post-stratification. Because not all sampled persons completed all portions of the survey, each individual represented in a public release file may have different sample weights assigned, depending on the nature of the non-response adjustments necessary. When using weights, it is important to select the correct weight variable (i.e. either from the Demographic file or from one of the other data files), namely the variable that applies to all members of the smallest analysis subpopulation.