A good poll is based on a scientific sample, i.e., persons are selected randomly and interviewers are told to interview these randomly selected people and no one else. A good poll also has a carefully written questionnaire that the interviewer follows to the letter. One of the best-known uses of polling is to predict the outcome of an election. Polls are also used to obtain opinions on subjects of national interest such as whether healthcare reform is needed or the federal government should do something about global warming. They are also used to test reactions to certain products or marketing campaigns.
Polls usually have rather small sample sizes.
This is sufficient precision for most purposes, even though the 1,000 respondents are a tiny fraction of the total population. Errors due to sampling are not the largest source of error in a survey, however. One very important problem that most polls face is the fact that many people simply will not participate. For a good poll, taken by a high quality survey research organization, the interviews are likely to contact over 1,500 potential respondents in order to get 1,000 to be interviewed. Many others refuse even to answer their telephone.