Note: This report was updated on Dec. 30, 2015 to reflect the January-July 2015 National Health Interview Survey estimates released on December 1, 2015. Telephone surveys face numerous challenges, but ...

One possible explanation for the variability in estimates across the different nonprobability samples is the range of methods that online sample vendors employ. They differ on recruitment, weighting ...

Survey research is an important form of scientific inquiry1 that merits rigorous design and analysis.2 The aim of a survey is to gather reliable and unbiased data from a representative sample of ...