Consequently, looking at an area s data over time is also valuable to a correct understanding of apparent changes in coverage. Where confidence intervals overlap, the observed difference might be due to chance. In these cases the estimate for that subgroup is not reported, but the individuals are still included in the overall sample and may have an effect on the overall estimate. National rates are based on the entire survey sample of more than 30,000 completed interviews. Race was self-reported by the respondent.
Hispanic children can be of any race.
An area s vaccination coverage estimate is based on the provider-verified responses from children who live in households with telephones. Complex statistical methods are used to adjust for children whose parents refuse to participate, those who live in households without telephones, or those whose immunization histories cannot be verified through their providers.