Date: Nov 2, 2000 11:02 AM
Author: Randy Poe
Subject: presidential polling theory?



Caught just a piece of a news story on the radio a couple of days ago,
where they were talking about the difficulties pollsters face trying
to get meaningful projections in this close US presidential race. One
pollster was saying that he knew of cases where two polls differed by
15 points in the same state, and he seemed to be implying that was
connected to the closeness of the race.

This started me wondering what sort of model could explain that.

We're trying to estimate p = the fraction of voters who will vote for
Gore. We do this by measuring p-hat, a fraction of people polled who
say they'll vote for Gore. Mostly I guess p-hat is assumed to be
normal with mean p and variance depending on sample size.

Obviously the sample has to be truly random and unbiased in some sense
for this to work, and presumably the polling companies have techniques
they use to try to eliminate bias. This guy seemed to be implying that
the nature of the race could either be introducing biases, or
increasing the variance of p-hat in some other way.

What could be going on here?

- Randy