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