What is the sampling error for the poll results?
Interviews with a scientific sample of 1 000 adults can accurately reflect the opinions of more than 185 million adults. That means interviews attempted with all 185 million adults – if such were possible – would give approximately the same results as a well-conducted survey. But what happens if another carefully done poll of 1000 adults gives slightly different results from the first survey? Neither of the polls is “wrong.” This range of results is called the error due to sampling, often called the margin of error. This is not an “error” in the sense of making a mistake. Rather, it is a measure of the possible range of approximation in the results because a sample was used. Pollsters express the size of the uncertainty caused by using a sample at a “confidence level.”This means a sample is likely to be within so many points of the results one would have gotten if an interview was attempted with the entire target population. They usually say this with 95% confidence. Thus, for example,
