For most of our national surveys of the general public, we conduct telephone surveys using a random digit sample of landline and cellphone numbers in the continental United States. Some of our surveys include additional, larger samples of subgroups, such as African Americans or young people (these are called “oversamples”). We also occasionally conduct surveys of people in particular states or regions, where our sample is limited to residents of these areas. Pew Research Center also conducts international surveys that involve sampling and interviewing people in multiple countries. Lastly, we sometimes survey special populations, such as foreign policy experts, scientists or journalists. In all of our surveys, we use probability sampling to help ensure adequate representation of the groups we survey.