A combination of landline and cell random digit dial (RDD) samples was used to reach a representative
sample of all adults the United States who have access to either a landline or cellular telephone. Both
samples were disproportionately-stratified to increase the incidence of African-American and Hispanic
respondents. Within strata, phone numbers were drawn with equal probabilities. The landline samples
were list-assisted and drawn from active blocks containing three or more residential listing while the cell
samples were not list-assisted, but were drawn through a systematic sampling from dedicated wireless
100-blocks and shared service 100-blocks with no directory-listed landline numbers.