Health departments use the data for a variety of purposes.
Respondents are identified through telephone-based methods. Although 95 percent of U.S. households have telephones, coverage ranges from 87-98 percent across states and varies for subgroups as well. These weights adjust for differences in probability of selection and nonresponse, as well as noncoverage, and must be used for deriving representative population-based estimates of risk factor prevalences. Unweighted data represent results before any adjustment is made for variation in respondents' probability of selection, for disproportionate selection of population subgroups relative to the state's population distribution, or nonresponse. However, it is not possible to accurately estimate the point estimates' confidence interval.