### 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, when and how to construct weights when combining survey cycles, and how to correctly create subsets within your analysis population.

### Overview: Weighting in NHANES

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

### Task 2: Constructing Weights for Combined NHANES Survey Cycles

In order to produce estimates with greater statistical reliability, it may be necessary to combine survey cycles to increase the survey sample size. If survey cycles are combined, new weights are needed.

- Key Concepts about Using Constructing Weights for Combined Survey Cycles
- When and How to Construct Weights for NHANES Analyses Across Survey Cycles

### Task 3: Creating Appropriate Subsets of Data for NHANES 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.

- Key Concepts about Creating Appropriate Subsets of Data for NHANES Analyses
- How to Create Appropriate Subsets of Data for NHANES Analyses in SUDAAN
- How to Create Appropriate Subsets of Data for NHANES Analyses in SAS

##### Contact Us:

- National Center for Health Statistics

3311 Toledo Rd

Hyattsville, MD 20782 - 1 (800) 232-4636
- cdcinfo@cdc.gov