How to Identify Correct Sampling Weights and File Locations

The table below shows sample weights that have been constructed for NHANES respondents included in the three different physical activity and cardiovascular fitness data files.  The table lists the types of sample weights by decreasing sample size.

NHANES Physical Activity and Cardiovascular Fitness Data Sample Weights and Data Files

Sample Size	NHANES Component	Physical Activity or Cardiovascular Fitness File	Data File Containing Sample Weight Variable	Weight Variable
Largest	Questionnaire	PAQ PAQIAF	DEMO	WTINT2YR
▼	Examination	CVX PAX	DEMO	WTMEC2YR
Smallest	Special subsamples (i.e., ½ sample for Cardiovascular Fitness (2005-2006)	CVX Subsample (2005-2006)	CVX (2005-2006)	Data not released at time of tutorial publication.

When combining any of the three data types, it is important to select the weight variable that applies to all members of the smallest analysis subpopulation. This will produce appropriate estimates adjusted for survey non-response.

For example, if you wish to combine data from the cardiovascular fitness and the physical activity questionnaire files, you must restrict your analysis to individuals with cardiovascular fitness data, which has the smaller sample size.  To do this, you must designate that persons with a non-zero examination sample weight value [variable WTMEC2YR in the DEMO (demographic) file] be included in the analysis. In doing so, you will be analyzing the physical activity questionnaire data for individuals who also completed the MEC examination.