Who does CHIS interview?
Every two years, the California Health Interview Survey conducts random-dial telephone interviews with up to 50,000 or more California households. The persons included in CHIS are a statistically representative sample of the entire state's diverse population. CHIS is especially known for its hard-to-find data on ethnic subgroups.
With each survey cycle, CHIS newly selects households to participate in the survey. Beginning in 2007, CHIS also includes a sample of cell-phone-only households - often younger and more mobile Californians frequently overlooked in land-line surveys. Such innovations help CHIS users learn more about an important sub-section of California's changing population.
How does CHIS work?
Computers randomly draw telephone numbers for 44 geographic areas that represent 41 individual counties and 3 groupings of counties with smaller populations. For each geographic area, CHIS has a targeted minimum number of people to include.
When CHIS contacts a household, one adult is randomly selected to be interviewed. Only that selected person can participate in each household. If there are minor children in the household, CHIS also asks questions about the adolescents and younger children.
Diversity
Additionally, CHIS uses many techniques to interview enough people from many ethnic groups to provide a strong basis for understanding most major and minor racial and ethnic populations that all are a part of California. Each cycle, thousands of CHIS interviews are conducted in languages other than English.
These downloadable tables show the number of people CHIS has interviewed for each county and race/ethnicity:
- CHIS 2007 Sample Size by County and Race/Ethnicity (PDF, 120k)
- CHIS 2005 Sample Size by County and Race/Ethnicity (PDF, 311k)
- CHIS 2003 Sample Size by County and Race/Ethnicity (PDF, 181k)
- CHIS 2001 Sample Size by County (PDF, 305k) Sample sizes for each racial/ethnic group (PDF, 308k)



