Who does CHIS interview?
Thousands of California households are selected each year as part of a scientific sample representing the entire state's diverse population. From each household, a random adult, teen and child are asked to participate in the California Health Interview Survey (CHIS).CHIS is well known for its hard-to-find data on special subgroups and provides relatively robust samples of the major racial/ethnic groups, LGB, and other populations living in California.
In 2007, CHIS began including a sample of cell-phone-only households. Residents of cell-phone only households tend to be younger, less likely to have health insurance coverage, engage in riskier health behaviors and are more mobile than those living in households with land-line telephones. Such innovations help CHIS accurately represent California's dynamic population.
How does CHIS work?
Computers randomly draw a sample of telephone numbers in each of 44 geographic areas (sampling strata) that represent 41 individual counties and 3 groupings of counties with smaller populations together. These areas represent the entire state.
When CHIS contacts a household, one adult is randomly selected to participate in the survey. In addition, a teenager (ages 12 to 17) and/or a child (ages 11 and under) may be randomly selected, depending on the household's composition. These teen and child interviews allow CHIS to track important health conditions and health behaviors of teens and children in California.
The large CHIS sample includes people from many ethnic groups to provide health-related information for most large and small racial and ethnic populations that all are a part of California. To represent California's diverse population and ensure that all ethnic groups can have a voice in representing the health of California, CHIS is conducted in English, Spanish, Chinese (Cantonese and Mandarin dialects), Korean, and Vietnamese.
These downloadable tables show the number of people CHIS has interviewed for each county and by race/ethnicity for each two-year cycle: