Why you shouldn’t trust polls
Yesterday, Gallup’s tracking poll showed Barack Obama with an 8-point lead over John McCain among registered voters, 48-40 — a result, Gallup believes, of the “bump” Obama received from positive media coverage of his overseas tour.
But today, a USA Today/Gallup poll of likely voters showed John McCain with a 4-point lead over Barack Obama, 49-45. Gallup notes that that’s a 10-point increase for McCain from last month’s poll of likely voters, which had him trailing Obama 50-44.
One might be tempted to chalk up the difference to the “likely” vs. “registered” pool of respondents. (But still…a 12-point discrepancy in polls taken over the same weekend?) But the USA Today/Gallup poll also showed Barack Obama with a 3-point lead over McCain among registered voters, 47-44, down from his 6-point lead in the June poll (48-42) — and far less than his 8-point lead in the other Gallup poll.
Note — both of these polls were conducted by Gallup.
The margin of error in both USA Today/Gallup polls was +/- 4 points; therefore both McCain’s 4-point lead among likely voters and Obama’s 3-point lead among registered voters fall within the margin of error.
Perhaps the headline should have read: “Obama, McCain Lead In Latest Poll.”
Gallup editor Frank Newport explained the discrepancy between the two Gallup polls as “statistical noise.”
Rasmussen’s tracking poll of 3000 likely voters over the weekend showed Obama with a 1-point lead.
RCP’s average is Obama +2.8.
Polls give us a snapshot in time, of the sentiments of the public, on the day the poll was taken. I don’t think they will mean much until after debates between Obama and McCain and the RNC and DNC conventions.
As will be pointed out ad nauseam over the next 97 days, the only poll that counts is the one in November. However, if I were McCain I would be concerned about the “registered voters” poll figures.
Here’s a quote from Chris Bowers to put this into perspective: “Outliers are an inevitable aspect of polling. One in twenty polls will be off by more than the margin of error, which in the case of most national polls is plus or minus three or four points for each person in the poll. That is, one in twenty polls will be off by at least seven points, and one in forty polls will favor McCain by at least seven points. Given that McCain had led in two of the last eighty polls according to Pollster.com, there is nothing surprising in the least about these results. An outlier in favor of McCain once every forty polls is an inevitable side effect of the most heavily polled election of all time. It would actually have been more surprising if there were no outliers in favor of McCain, ever.” http://www.openleft.com/showDiary.do?diaryId=7206
In other words, McCain has had a lead in only two of the last 80 polls, which is what one would expect just by understanding statistics, but that doesn’t stop conservatives or pundits (who want a tie for the sake of their ratings) from making a big deal out of outliers like this one.
Also worthy of note, the pollster.com average “shows Obama ahead 47.0%-41.9% nationally.”
If I were Obama, I’d be worried about the “likely voter” polls.
Wow, McCain leads in a poll and we suddenly get an article explaining why we shouldnt believe polls, coincidence? I think not.
Polls are inherently flawed, most suffer from oversampling of one party over the other, or a large sample of “independents/non-decided” voters.
Centrist and Si Vis, too bad that you can’t (or don’t want to) read previous comments. When Obama leads in 78 out of 80 polls, that means that Obama is leading. There is a 5% chance for any poll that the actual numbers are outside of the margin of error, so 2 out of 80 doesn’t mean anything whereas 78 out of 80 does.
Adam, so what? Obamessiah leads in the polls! Lets just anoint him President for 10 years and be done with it! After all, polls are ALWAYS correct, right? See Dukakis, Mondale, Gore and Kerry for proof that polls are always right.
My point was this article would NOT have been written had it not been for the two outliers, if all the polls pointed to The Chosen One, nothing would have been said.
I’m 54 and I’ve never been polled for anything.
I’m 54 and I’ve never been polled for anything. I’m Voting for McCain.