### 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 I

Weights are created in NHANES I to account for complex survey design (including oversampling), survey non-response, and post-stratification. When a sample is weighted in NHANES I 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 I
- 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 I
- How to Select the Correct Weight in NHANES I

### Task 2: Creating Appropriate Subsets of Data for NHANES I 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.

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