Notice How Much Better President Obama Does When Cell Phone Respondents Are Included

[DemocratSinceBirth]

http://www.surveyusa.com/client/PollReport.aspx?g=ac0d63ea-75f1-42aa-ba9c-e6955f64c76b

That should make you think twice when interpeting polls by pollsters that only include those with landlines. Those pollsters include
We Ask America, Rasmussen, Gravis, and even our friends at PPP.

These pollsters weight their results to compensate for the fact they don't call those with landlines but weighting introduces problems of its own,ergo:

At a minimum, excluding cellphones means these polls are increasingly reliant on statistical weighting. They might make up for a lack of young people, for instance, by counting several times the answers from the few younger respondents. Peter Miller, a recent president of the American Association for Public Opinion Research, points out the root problem with weighting: “The more you rely on weights, the more you risk being wrong for reasons you don’t understand.”


http://www.washingtonpost.com/opinions/five-myths-about-political-polls/2012/10/12/21408264-13de-11e2-ba83-a7a396e6b2a7_story_1.html