They are an attempt to determine who may actually win an election in advance of the final vote. Let's say that 100 million people are expected to vote in the general election. If 100 people are asked for their opinions, each respondent represents a million voters. Obviously , the results of such a poll are not very reliable . The more people surveyed, the more meaningful are the results.
Pollsters have various ways of making their polls more accurate .
They try to find a representative variety of people to question. For example, they look for people with similar backgrounds and from similar regions to those of all the voters. Pollsters also ask questions that try to determine how many people who support each candidate will actually vote. If a candidate has a higher percentage of enthusiastic supporters than his opponent, he has a better chance of winning than the simple numbers might suggest. If we look at polls that are taken over time, we can often detect a trend .