A poll average is the result of someone taking the combined information from many different
opinion poll
An opinion poll, often simply referred to as a survey or a poll (although strictly a poll is an actual election) is a human research survey of public opinion from a particular sample. Opinion polls are usually designed to represent the opinions ...
s that deal with the same issue and synthesizing the information into a new set of numbers.
[Lynch, Scott M. Introduction to Bayesian Statistics and Estimation for Social Scientists (2007)]
The problem with this is that each poll is usually conducted in a slightly different manner, which technically cannot be combined into one poll. Polls in themselves contain uncertainty because they are only using a sample of the population. The
uncertainty
Uncertainty refers to epistemic situations involving imperfect or unknown information. It applies to predictions of future events, to physical measurements that are already made, or to the unknown. Uncertainty arises in partially observable or ...
is measurable, which we usually call the
margin of error
The margin of error is a statistic expressing the amount of random sampling error in the results of a survey. The larger the margin of error, the less confidence one should have that a poll result would reflect the result of a census of the ent ...
. An inaccurate way to conduct a poll average is to treat each poll as though they were exactly the same in uncertainty. The reason for this is that this type of poll average gives less weight to the polls that have less uncertainty.
However, if you account for the variation in polls due to each poll's unique sample size, you can combine the polls into a poll average. This means the only assumption you are making is that each poll was conducted in a similar manner. You can also measure the uncertainty of this poll average.
References
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External links
2008 Presidential Election poll average
Polling