Why are the pollsters estimates of uncertainty larger than the ones calculated by TruthIsAll and others?
TruthIsAll sometimes has argued that the exit polls should be treated as simple random samples (like drawing marbles from a hat). In this instance, the margin of error for Ohio, with a reported sample size of 2040, would be about 4.5 points on the margin using the 95% standard. There are two problems with this reasoning. First, the exit polls are not simple random samples; they are limited to a relatively small number of precincts (49 in Ohio), and this limitation increases the statistical uncertainty. Second, the pollsters do not use a textbook formula to calculate their margins of error. Instead, they examine the actual deviations of their exit poll samples from past results in the same precincts. Ideally, all these deviations would be of the same size, in the same direction. (For instance, hypothetically, the poll might show Bush doing 2 points better everywhere in 2004 compared to 2000 — although a result that neat would be extraordinarily unlikely.) The greater the variability in
TruthIsAll sometimes has argued that the exit polls should be treated as simple random samples (like drawing marbles from a hat). In this instance, the margin of error for Ohio, with a reported sample size of 2040, would be about 4.5 points on the margin using the 95% standard. There are two problems with this reasoning. First, the exit polls are not simple random samples; they are limited to a relatively small number of precincts (49 in Ohio), and this limitation increases the statistical uncertainty. Second, the pollsters do not use a textbook formula to calculate their margins of error. Instead, they examine the actual deviations of their exit poll samples from past results in the same precincts. Ideally, all these deviations would be of the same size, in the same direction. (For instance, hypothetically, the poll might show Bush doing 2 points better everywhere in 2004 compared to 2000 — although a result that neat would be extraordinarily unlikely.) The greater the variability in
