Surveys or Polls: The word survey or poll usually describes a method of gathering information from a sample of individuals. In contrast to a census, where all members of the population are studied, surveys collect details from only a part of a population of interest. The size of sample will mainly depend on the aim of the study. In a statistically valid survey, the sample is chosen so that each person in the population has a measurable chance of participating. This allows the analyst to reliably project from the sample to the larger population.