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Excellent work. For long time Freepers, the inaccuracy of polls is well known. The MOE of a poll is greatly misunderstood by the public. MOE refers only to the precision of the poll and has nothing to do with the poll's accuracy. Technically precision is a measure of how a particular polling methodology will give the same result if conducted over and over again. For instance if a polling company conducted the same poll three times on the same day, each of the three polls should give the same results within the MOE. Accuracy on the other hand refers to whether or not a particular measurement (poll) is correct or gets the right answer. Precision (MOE) has nothing to do with accuracy. For a poll to be accurate, the polling sample must be unbiased, meaning the people polled must be statistically representative of the actual electorate. Pollsters realize that they never have a truly unbiased sample. Consequently, they try to compensate for the bias inherent in their methodology, but fudging the raw poll results, by correction factors. The only way for a pollster to determine these correction factors is to do the same analysis you have done on their own polls.

In conclusion polls are not to be trusted. Polls with an MOE of 3% may be inaccurate by 20% and the public has no way of knowing the accuracy of a poll until after the election. Tracking polls have some limited value in showing trends, because movement from one candidate to another is somewhat independent of the sample bias and of the pollster's correction factors. Only the direction of the trend is somewhat reliable, since the magnitude of the trend is dependent on the sample bias and the pollster's correction factors. Unfortunately, trends are often only a few percentage points and therefore are under the polls MOE making them meaningless.

Thanks for your thoughtful reply. As already mentioned on the thread, as a member of the general public, I take an MOE to be exactly what the media and pollsters represent it to be — a range of percentage points within which a given poll result can be considered to be accurate. Your point that MOE's are greatly misunderstood by the public goes to heart of my premise: That the public has absolutely no way to verify the accuracy of most polls.

What I have done in a kind of big way is to reflect exactly what the general public, most in the media, and even pollsters, themselves, do after every election. Election after election, people routinely look at the last polls that came out, compare them to the actual election results, and make judgements about which polling organization was the most accurate based on whose poll percentages came the closest to the actuals. In other words, they do exactly as I have done in this case study. Except in this case, I looked at 20 polls instead of just a handful.