Task 1: How to Select the Correct Weights for NHANES III Analysis

To select the correct weights for NHANES III data, you need to first check all variables in your analysis and select the weight of the smallest analysis subpopulation.  Separate weights are provided for those who completed the interview, MEC exam, MEC + home exam, or are part of one of 4 subsamples (AM exam subsample, PM exam subsample, allergy or central nervous system (CNS) exam subsample). See the Table below for the correct weights for each component.


Appropriate Uses of the NHANES III Sampling Weights

Table of Appropriate Uses of NHANES III Sampling Weights


It is important to check all the variables in your analysis and use the weight of the smallest sample subpopulation. Otherwise you will not obtain estimates appropriately adjusted for survey non-response.



Unlike continuous NHANES, for NHANES III there is no need to construct weights when looking at both phases combined, however, you must be careful to determine whether any variable in the analysis was only measured in a single phase of NHANES III. In addition, you must verify that variables were measured comparably in both phases of the survey before combining phase data. All weights (exam weight name being used in this example) are provided for Phase 1 (1988-1991 — wtpfhx1), for Phase 2 (1991-1994 — wtpfhx2) or the combined 6 year data set (1988-1994 — wtpfhx6).


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