Wrong Element
Sentient Onion
- Joined
- May 5, 2002
- Posts
- 24,909
I read the results of the most recent Monmouth poll in Ohio and it prompts me to say something here about polling in general. The raw vote in that random poll showed Trump ahead by two. The pollster weighted the results, which is something virtually all pollsters do, and announced Clinton is ahead by four. The pollster may be right about that, but the pollster may also be wrong. It's really nothing more than a guess. Perhaps an informed guess, but still a guess. I suppose the pollster thought it was a bad sample. Maybe it was. Maybe it wasn't. Nobody really knows.
I still like the methodology of the USC/LA Times poll. It's basically the same sample over and over again. Good or bad. And nobody knows whether it's a good sample or a bad one, at this point.
The main reason a pollster would do that is that if you take polls with small sample sizes -- and the Monmouth poll is fairly small, just 400 people -- you're not always going to get a representative sample every time. The idea of the weighting is to avoid wild swings that aren't measuring real changes in public opinion, but rather a fluke with the sample.
So a pollster might say, prior to doing any polls for the presidential race, "We're saying that the electorate is 1/3 Democratic, 1/3 Republican, and 1/3 independent," and amend their raw data accordingly, since the chance you're going to get that exact breakdown in a poll of 400 people is not good. They might be wrong about the makeup of the electorate -- which is how Gallup got into so much trouble four years ago -- but it's obviously in their interest to get it right.
Looking at the raw data from the Monmouth poll, they obviously felt they had too few Democrats and too many Republicans in their sample (the number of independents was pretty close to what they are aiming for).
Again, maybe they're just wrong about how many Ds and Rs there are in Ohio, in which case they will look pretty stupid in three months. But the 4-point margin for Clinton is more in line with the other poll of Ohio that came out today, the CBS News poll that showed Hillary up 6.