With the U.S. presidential election on November 6, we are
presented with an ever increasing onslaught of political polls
and their results. To make a proper interpretation of a poll’s
results, three additional variables should be specified in
addition to the proportion results: the poll’s margin of error,
the desired level of confidence, and the sample size. In this
brief essay, I will review the math behind the margin of error
in polls to help you with interpretation of polls. The purpose
of a poll is to estimate the opinion or behavior of a population
from a sample. We work with a sample since contacting the entire
population is too time consuming, often too expensive, and can
be physically impossible. Several methods of sampling are used,
and simple random sampling, systematic sampling, stratified
sampling, and cluster sampling are the most widely used methods.
After the sample is selected from the population, a statistic
computed from sample information estimates a population
parameter. The statistic comp