Charles Franklin at Pollster.com responds today to reader claims that Rasmussen skews poll averages of President Obama's approval rating by turning in numbers that are consistently 2-3 points below the average.
It's true--Rasmussen's daily polls are low (see the graph below), but Franklin points out that Gallup's daily polls are also consistently high, and the two balance each other. Pollster.com's overall average, meanwhile, is remarkably close to the average of non-daily polls, published by a heterogenous group of 23 different firms.
So its just a matter, as Franklin says, of picking one's poison. More broadly, it raises an epistemological question about the nature of polls and skewed data: how does one know that polls like Rasmussen's are low, or that Gallup's are high? One would have to know Obama's true approval rating, in a rationalistic sense that doesn't mesh with the empirical process of poll-taking.
In other words, you can exclude a poll that's lower than the average because you think it's low, but that's exactly what you're doing--selectively altering the data and driving up the trend.
Why these guys continue to cover for Rasmussen is a bit of a mystery. He's not two or three points off on approvals he's ten or eleven points off the max appros. He also has non appros in the mid forties while every other poll out there including Fox has them in the 25-30% range. That means his disappros are between 15 and 20% off. This is not statistical noise. Gallup has Obama at 63% approval which is right in the middle of some six polls that have been published in the last eight days excluding Rassmussen. Gallup is not overstating his numbers.
Thanks to ottovbvs for pointing out the fallacy of this non-defense of Rasmussen. Somehow everytime someone calls Pollster out on this, they ust show the approval graph and not the non-approval graph where the discrepancies between Ras and non-Ras polls are in 15-20% range and not 2-3%!
Also, these defenders conveniently ignore that Ras uses a Likely voter screen more than 3.5 years before the next Pres. election, what utter nonsense.
I would greatly appreciate it if Mr Good could explain the concern raised by this comment posted on the Pollster link:
All polls minus Rasmussen, Gallup, PPP and Internet (numbers in parenthesis include USA Today/Gallup):
Approve 61.6% (61.7%)
Disapprove 30.1% (30.0%)
+31.5% (+31.7%)
Just Gallup (numbers in parenthesis include USA Today/Gallup):
Approve 61.7% (62.0%)
Disapprove 29.7% (29.6%)
+32.0% (+32.4%)
Just Rasmussen:
Approve 54.4%
Disapprove 44.9%
+9.5%
Just PPP:
Approve 53.0%
Disapprove 41.0%
+12.0%
Conclusion:
Gallup is 0.5 points off the mark of ALL the surveys minus Gallup, Rasmussen, PPP and the Internet-only ones.
Rasmussen is 22 points off the mark.
PPP is 19.5 points off the mark.
It seems to me that Gallup is actually pretty much right on track with the average of all the other polls, while Rasmussen and PPP are way, way, way off the mark.
Judging by that, I don't know how any one can seriously take the numbers Rasmussen and PPP are presenting seriously.
Gentleman, please call up anyone who relies on political polling for a living and ask them whether they think Scott Rasmussen's work is a farce. No, seriously, do it. Then come back and tell us about how Gallup is more accurate and isn't laughably oversampling liberals because it is in their vested (liberal) interest to further the strength of the President.