Environmental Chemical Data Structure and Content
Purpose
This module provides an overview of the structure of the environmental chemical data and the content in the National Health and Nutrition Examination Survey (NHANES).
Task 1: Describe How the Environmental Chemical Data Fit into the NHANES Data Structure
Before you begin a search for any specific environmental chemical variables on the website, you should first understand the NHANES data structure and how environmental chemical data files fit in. This task describes how the environmental chemical data files fit into the NHANES data structure and why you need to understand NHANES data structure before you begin analyzing the data.
Task 2: Describe Environmental Chemical Data Files
The environmental chemical data are found in the Laboratory section. These laboratory data require unique collection and data processing before the data are released to the public. This task describes the steps in this process including: establishing a survey sample, defining exclusion criteria, collecting the data, processing the data, and preparing and editing the environmental chemical files.
Task 3: Describe Non-Probability Based Environmental Chemical Data Files
Some environmental analytes from NHANES were measured in a non-probability-based or "convenience” sample. For those analytes that are measured in a non-probability-based sample, care is needed when interpreting the results. Inference from these analyses is limited to those respondents in the sample and they are not representative of the U.S. population. This task explains the limitations of such samples.