Monday, October 1, 2012

Skewed political polls?

Update, October 17: Here's a link to Nate Silver's more serious NY Times column on the temptations, and risks, of cherry picking poll results.

Here's a link to Nate Silver's take on the skewed polls claim. The bottom line? Over the last few decades of political polling, the polls have been pretty balanced, making mistakes in one direction one year, and in the other in other years. Four years ago, they got the presidential election exactly right. Silver points out that the "oversampling" criticism is "largely unsound." He goes on:
But pollsters, at least if they are following the industry’s standard guidelines, do not choose how many Democrats, Republicans or independent voters to put into their samples — any more than they choose the number of voters for Mr. Obama or Mitt Romney. Instead, this is determined by the responses of the voters that they reach after calling random numbers from telephone directories or registered voter lists.
Pollsters will re-weight their numbers if the demographics of their sample diverge from Census Bureau data. For instance, it is typically more challenging to get younger voters on the phone, so most pollsters weight their samples by age to remedy this problem.
But party identification is not a hard-and-fast demographic characteristic like race, age or gender. Instead, it can change in reaction to news and political events from the party conventions to the Sept. 11 attacks. Since changes in public opinion are precisely what polls are trying to measure, it would defeat the purpose of conducting a survey if pollsters insisted that they knew what it was ahead of time.
For another take on the issue, see this Stephen Colbert segment (I've linked it as well as embedded it).

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