NHANES III data files are released by their collection method, and as supplemental data files. Many of these are very large data files with many variables. Most analysts will only need a few selected variables. You will likely wish to keep only those variables when you create your analytic dataset. This process is called keeping.
- Key Concepts about Keeping Data in NHANES III
- How to Keep NHANES III Data
- Download Sample Code and Dataset
The basic data files were organized by their collection method, which can fall under one of four components: Examination, Laboratory, Adult or Youth Questionnaire, or Foods. To allow for timelier releases, supplemental data files (component updates and specialized sub-sections of these components) were released at later dates as they were completed. Joining the components of the data files is called merging.