Let’s begin by reviewing some terminology that you have probably seen elsewhere. A survey asks questions of a subset of people who belong to a much larger group called the population. The subset of the population that is included in the survey is called a sample. When done correctly, a survey reveals characteristics of the population, avoiding the need to contact every member of the population. A sample that presents a snapshot of the population is said to be representative. Samples that distort the population, such as one that systematically omits a portion of the population, are said to have bias.