Key Concepts About Identifying Variable Names and File Locations

Variables are stored in different data files. Data files are organized by their collection method, which can fall under one of five components: Demographic, Dietary, Examination, Laboratory, and Questionnaire. Usually, analysis will require more than one component. For instance age and gender are in the Demographics component, while blood pressure measurements are in the Examination component, cholesterol variables are in the Laboratory component, and questions about previous diagnoses or taking medications for hypertension are in the Questionnaire component. All these variables would be required in a complete analysis of cardiovascular disease.

Data for different components of the survey are released in separate data files to facilitate a more timely data release and faster access over the Internet. Below is a list of the file types and a summary of their contents.

• Demographics files: survey design (e.g. weights, design strata) and demographic variables
• Dietary files:  data collected from participants on their dietary intake, which includes foods, beverages and dietary supplements.
• Examination files: information collected through physical exams, dental exams, and dietary interview components  (Note: not every survey participant agreed to a physical examination)
• Laboratory files: results from analyses of blood, urine, hair, air, tuberculosis skin test, and household dust and water specimens
• Questionnaire files: data collected through household interview and mobile examination center (MEC) interview

The component's variable list contains the list of all the publicly released variables and their file locations. The variables lists are available as web pages and list the

• filename the variable is found in,
• name of the component,
• variable name, and
• variable's English label (a short description of the variable).

Use the find feature to speed up your search for variables relevant to your analysis. This feature is most likely found under the Edit option of the topmost toolbar of your browser. Otherwise, try pressing the Control key and F at the same time. The search box to enter your keyword should appear  near the top or bottom of your browser. Not every result returned will be relevant to your analysis. Note the file names that the variables are stored in, you will use this to identify the data file and documentation to download. The data file documentation (discussed in the next task) will guide to include the appropriate variables for your analysis.

For example, there are two sets of cholesterol variables - Total Cholesterol and HDL Cholesterol and Standard Biochemistry Profile. You have identified the variable names (LBXTC and LBXSCH) and file names (l13_b and l40_b), so now you can consult the data file documentation to learn which variables to use in your analysis.

All variables listed in the component variable lists have been publicly released and are available for download in the associated data file. If you wish to use a variable that is not listed in a component variable list, you will need to use the Research Data Center. You can review the Research Data Center for more information about how to obtain access to non-publicly released variables.