BRFSS Methodology Changes in 2011
Starting in 2011, BRFSS protocol requires that the NJBRFS incorporate a fixed quota of interviews from cell phone respondents along with a new weighting methodology called iterative proportional fitting or "raking". The new weighting methodology incorporates additional demographic information (such as education, race, and marital status) in the weighting process.
These methodological changes were implemented to account for the under-representation of certain demographic groups in the land line sample which resulted in part from the increasing number of U.S. households without land line phones.
Comparisons between 2011 and prior years should therefore be made with caution.
More details about these changes are available from the CDC:
- Changes to the Behavioral Risk Factor Surveillance System FAQs
- Methodologic Changes in the Behavioral Risk Factor Surveillance System in 2011 and Potential Effects on Prevalence Estimates MMWR Report