Let's consider the California Health Interview Survey (CHIS), which is conducted by the UCLA Center for Health Policy Research, the California Department of Public Health, and the Public Health Institute. The CHIS uses a multistage sampling design with California partitioned into 44 geographic regions. Within each of the 44 regions, randomly generated digits are used to select both cell and landline telephone numbers. Subjects are called and interviewed by phone. For a recent , 1, 845 subjects were surveyed, including 20,724 adults ( ages 18 and older) , 1,201 adolescents (ages 12-17)and 2,920 children ( ages 0-11. For a recent CHIS, the response rate is approximately 15%, although the complexity of the sample design makes it somewhat difficult to accurately describe the response rate with a single percentage