What is public opinion and how is it measured - what factors make public opinion pools accurate and what factors cause them to be inaccurate?

Public opinion is simply the various views that citizens hold regarding a wide variety of issues. A very simple example is "Do you approve of the job President Bush is doing?" Politicians often hire polling firms to find out where public opinion lies on various issues so that they can govern according to the people's desires (at least in theory). Public opinion polls are made more accurate by polling a large number of people. A poll would be perfectly accurate if it polled every person in the country, but that's obviously impossible, so a smaller group is polled in the hopes of estimating the opinion of the entire population. Usually it's only 500 to 1000 people. The smaller that group is, the less accurate is the estimate of the true opinion on an issue. This is why most polls have an "error margin" shown of say plus or minus 4% -- this means that the pollers are reasonably sure that the true answer is within 4% of the answer given by the group. So if 500 people are polled and 35% approve of the job George Bush is doing, the true answer for the whole population is almost certainly somewhere between 31% and 39%. If 1000 people are polled the error margin would be less than 4%. Polls are also made more accurate by ensuring that all groups are represented (male/female, old/young, white/black/Hispanic, etc.) If you ask the Bush question in rural Texas, you'll get a very different answer than in New York City, so it's important to try to get a poll group that represents the population as a whole. Polls get less accurate if there are lots of possible answers to a question instead of a simple yes/no. A good example of this is asking people which one of the dozen or so presidential candidates in each party they support. The error margin will be a higher for this question than for the Bush question above. Hope this helps!