These surveys ask people how they identify their religious beliefs or what religious groups they are affiliated with. Answers depend on what options they are given and how many people are surveyed. Results vary widely. For example, people who say they are Christian may then be given a list of denominations to choose among, or they may be given categories that include such terms as evangelical or Pentecostal. Some ask people questions over the phone or in person, while others gather data from religious groups that keep track of their own numbers. Each has its strengths and shortcomings, and most journalists find some surveys’ categories to be more trustworthy than others.