Polls

I think DJ Drummond at Wizbang must be quite the student of polling and polling statistics.  He has been having lengthy posts about the polls for this election.  Including this one.

You'd think running a poll would be pretty straightforward.  You call up a bunch of people and ask them who they're voting for, right?  Not so fast.

As the pollsters at the Liberty Digest learned in the last century, you have to make sure you're polling a representative sample of the voting population.  This can be a lot easier said than done.

One of Drummond's (and many others') complaints about the polls is the extent to which they over-sample Democrats in their surveys. When your sample is biased 2:1 in favor of Democrats, it's not surprising the result would show Obama leading.  Or is it?

Maybe that's what you were able to get.  Maybe all the Republicans were out working overtime, or taking kids to their soccer games, or whatever.  Maybe the majority of people taking leisure time at home were Democrats.  All isn't necessarily lost.  If you know how the proportion of the voting public is Republican and Democrat, you can weight the answers and re-composite them to reflect the actual voting numbers.  Assuming your guess as to who'll be voting this time around is right.

But Drummond has some other comments about possible biases in the polls, including one that might be worth sipping:

I have already written extensively about polling groups manipulation of demographic weights, so I will only summarize here that in addition to party affiliation, various polling groups this year have produced polls out of demographic balance with Census norms for urban/suburban/rural participation, minority race representation, age, employment status, and income range. It should not be difficult to imagine how these manipulations might invalidate the results published by the polling groups.

When people reach this point in the discussion, an obvious question comes up; surely the polls want to be accurate, and they would have to understand that this fiddling with internal data to create a false image would destroy their credibility? And the answer to that can be phrased in a two-reminder of just how stupid people can be - "New Coke".....

This brings us back to the polls. The thing most folks forget about polls which get published in the media, is that the polls' first need is not to accurately reflect the election progress and report on actual support levels; it's about business. A poll needs clients to survive, and the media - always - wants a good story more than they want facts. So polls sell that story, and what would actually be a gradual development of support, with modest changes brought about as the public learned about candidates' records and positions, is instead sold as an exciting roller-coaster race, careening madly all over the place. If a candidate appears to be popular and charismatic, he might be allowed a strong lead, or the poll might tighten things from time to time just to keep attention on the polls....And when you take apart the polls and drill down to the raw data, what you find is a close race with a gradually declining but still large pool of undecided voters, which is consistent with the known facts and actions we see from both campaigns.

....

This year, trying to gauge the effects of Barack Obama's 'rock star' charisma, Gallup decided to abandon historical norms and overweight urban and youth voters, and to over-sample democrats all campaign long. This model, dubbed the "expanded voter", has proven a disaster for Gallup, so much so that the group reintroduced a more historically balanced model, which they call the "traditional" model. The problem for Gallup, however, is that their methodology became so skewed throughout the campaign up to now, that it may be impossible for Gallup to correct its procedures before the final election poll. In the light of past blunders, this year missing the call may not be unreasonable at all to expect.

....

What I think is happening, is this - the polls' headquarters were based deep in liberal territory, where the assumption was that Obama's candidacy would actually create a groundswell of pro-democrat voters unseen in the country since 1932. That McCain is more experienced with the key issues than Obama was ignored, that the historical significance of the debates shows that the effects appear several weeks later was also ignored. That the economy could be as reasonably blamed on the democrat-controled Congress as on the republican President was never considered. That character would be a salient factor in the decisions of voters was rejected out of hand.

The polls are wrong. Make your own mind up, because your vote will matter.