Task 2: How to
Identify Variable Names and File Locations
To identify the variable names and file locations for the
variables in your analysis, you will need to check the variable list
for four of the five components:
- Demographics
- Examination
- Laboratory
- Questionnaire
Step 1: Demographics
First, you will check the demographics variable list to
identify the age and gender variable names and file names.
If you are still at the PDF file of the laboratory survey
documentation, click your browser's Back button twice to return to
the NHANES 2001-2002 page. If you returned to the NHANES homepage,
click the Questionnaires, Datasets, and Related Documentation link in the navigation menu, then click
the NHANES 2001-2002 link.
Click the Demographics link, then click the
Demographics Variable List link. For your analysis you need the age and
gender variables. Find them on the list and note the variable names, their SAS
labels, and the file name that the variables are in. Your notes might look like
the table below.
Example Notes from Data Documentation
| Item |
Label |
Variable |
File Name |
| gender |
Gender - Adjudicated |
RIAGENDR |
DEMO_B |
| age |
Age at Screening Adjudicated - Recode |
RIDAGEYR |
DEMO_B |
Step 2: Examination
Now, you will find the examination variable list and locate the
variables that contain blood pressure measurements and apply to your
analysis.
From the Demographics variable list, click your browser's Back
button twice to return to the NHANES 2001-2002 page. Click the
Examination link, and then the Variable List link.
This web page has many more variables than the Demographic variable
list, so use the find feature to locate variables related to
"blood pressure." Note the variable names, their SAS labels, and the
file name that the variables are in.
Step 3: Laboratory
From the Examination variable list, click your browser's Back
button twice to return to the NHANES 2001-2002 page. Click the
Laboratory link, and then the Variable List link. Use
the find feature to locate variables related to "cholesterol."
Note the variable names, their SAS labels, and the file name that the variables are in.
There will be four data files with cholesterol variables
— l13_b, l13_2_b, l40_b, and l40_2_b. You will need to
consult additional documentation to determine which one is appropriate for use in your analysis.
Step 4: Questionnaire
You should also check the Questionnaire variable list to
determine which questions pertain to previous hypertension diagnoses
and if the sample person is taking mediation or action to control
his/her blood pressure. You'll do this one on your own and check
your work when you are finished.
Please note that you may find multiple results when searching for your variables. For instance, the results on the search "cholesterol" will render results from both Total Cholesterol and HDL Cholesterol and Standard Biochemistry Profile and their Second Day Lab counterparts. You should always read the documentation carefully in order to select appropriate variables for your analysis. The documentation recommends that you to use serum total cholesterol and HDL from Total Cholesterol and HDL Cholesterol, which contains total cholesterol results using the reference analytic method, rather than Standard Biochemistry Profile, which also has total cholesterol as part of the general chemistry. For LDL and Triglycerides, the documentation recommends that you use data from Triglycerides and LDL-Cholesterol, which is the morning fasting subsample, as the fasting values on LDL and Triglycerides are the appropriate ones to use for analysis. The Second Day lab files are based on a convenience sample and can be used to determine intra-individual biological variation for methodologic studies.
Close Window to return to module page.
IMPORTANT NOTE