### Purpose

This module addresses why weights are created and how they are calculated, the importance of weights in making estimates that are representative of the U.S. civilian non-institutionalized population, how to select the appropriate weight to use in your analysis, and how to correctly create subsets within your analysis population.

### Overview: Weighting in NHANES III

Weights are created in NHANES to account for the complex survey design (including oversampling) and survey non-response and are post-stratified to Census Bureau population estimates. When a sample is weighted in NHANES III it is representative of the U.S. Census civilian non-institutionalized population. A sample weight is assigned to each sample person. It is a measure of the number of people in the population represented by that sample person.

- Key Concepts about Weighting in NHANES III
- Examples of the Effect of Not Including Sample Weights in Analyses

### Task 1: Selecting the Correct Weight

To produce estimates appropriately adjusted for survey non-response, it is important to check all of the variables in your analysis and select the weight of the smallest analysis subpopulation.

- Key Concepts about Selecting the Correct Weight in NHANES III
- How to Select the Correct Weight for NHANES III Analysis

### Task 2: Creating Appropriate Subsets of Data for NHANES III Analyses

In order to calculate the most accurate measure of the variance estimate, it is important to properly create subsets of your data to reflect the subpopulation of interest before using weights in your analyses.

The contents in the Continuous NHANES tutorial on this topic are applicable to both continuous NHANES and NHANES III data. Please consult the main tutorial for more detailed information.

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