The "margin of error" or plus/minus percentage figures that accompany
most media reports of polls reflect the size of the final sample.
The only perfect poll of the American public would be one that interviewed everyone
in the United States.
Short of that, we're making an approximation. The more people you have in your sample,
the better your approximation. When pollsters use the word "error,"
it doesn't mean they're wrong, it just means they might be wrong. What this
figure does not reveal are the sampling methods or the extent to which the
targeted individuals or households were actually included in the final sample.
And this is where reporters almost always get it wrong. Most polls that the
media report have a margin of error of 3 points if it's a good poll, and 4 or 5
points if it's a quickie poll (or a poll done only of a subset of the
population, like Democrats or women). You will almost never hear someone on the
news describe a 1 or 2 or 3 point lead as anything but a "lead," when
in fact it's a tie. And as seen in the last few presidential elections, candidates rarely lead by more than six points.
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