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Has anyone combined the 1999-2002 data with the 2003-2004 NHANES data?
I'm using the 4yr weights for the 99-02 but I'm not sure what to do with the 2yr weights on the 2003-2004 data - there don't appear to be updates with 6yr weights. How do I handle the weights when combining 03-04 with the earlier data?
This document on the NCHS website tells you how to create a 6-year weight:
For an estimate of the 6-year 1999-2004, a 6-year weight variable can be created by taking 2/3 of the 4 year weight for each sampled person in 1999-2002 and 1/3 of the 2 year weight for each sampled person in 2003-04.
The document doesn't have page numbers, but this is towards the end of it (~15 page document).
NCHS has created a tutorial for using the NHANES data, which you might find useful: