How do Presidential "polls" work?

this is a very broad question… there are numerous organizations who poll widely varying sections of the population using several different methods. one common polling method is to call a theoretically random slice of registered voters who are listed in the telephone book, and ask them who they plan on voting for. every poll has its own method of choosing who to call.

you are quite right to be worries about accuracy, since a huge number of people don’t have landline phones anymore (particularly folks under the age of 30…)

Polls also predominately poll in urban areas and during the day, which may then skew the results to the unemployed and to less conservative, urban respondents.

You may not want to research it this much, but here is a link that you may find useful.

http://www.newsu.org/Angel/section/default.asp?format=course&id=aapor_polling07

It is a full course on polling it’s free and you can browse the links as they interest you.

it’s pure statistics!

Ohhhh. Thanks Gooch. It all makes sense now.

glad to help Chris

Chris, sorry it took me so long to respond to this question. I’ve been away and * gasp * not checking Fluther. Anyway, here are the basics.

Public opinion polling is, essentially, like drawing randomly from a box full of marbles. Imagine a big box full of marbles of different colors, all mixed up. If someone asked you, “what percentage of marbles in the box are red?” you could tip the whole box over and count all the marbles and see how many are red. But, if you don’t have time for that, or if the box is just too huge to do that, instead you could pull out a random sample of marbles from the box. So let’s say you reach in and pull out 10 marbles from the box and of those 10, 5 are red. You could answer the question by saying, “my best guess is that about 50% of the marbles are red.”

How accurate is your estimate? Well, in this case, not super accurate because you don’t have a very big sample (in fact, statistically, we would say that you are 95% confident that the actual percentage of red marbles in the box is between about 20% and 80%, not a particularly useful margin). But, as your sample size increases, your potential for error decreases. If you reached in again and drew out 100 marbles and 50 of them were red, then you could say, “I’m 95% confident that the actual percentage of reds in the box is between 40% and 60%.”

Public opinion polling is basically just a more sophisticated version of this. Instead of a box, we have a pool of potential voters, each of whom has a “color” (i.e. their presidential preference). Most polls reach in and draw out between 400 and 1200 voters from this pool and as a result they make an estimate from this sample. You might notice that polls with larger sample sizes have smaller margins-of-error. This is because of the principle noted above: larger sample size means less potential for error.

As elections draw nearer, many polling outfits go from drawing their samples from Registered Voters to “Likely” voters. This just means that pollsters are drawing their marbles out of a different box. “Likely” voters is somewhat subjective, so this absolutely introduces more potential for error which is not captured in the margin-of-error, though probably not very much since these polling firms test and retest their models for predicting likely voters.

Finally, there is the issue of cell-phone use. Sam is correct that a growing number of people don’t have land-lines. This could be a problem because most pollsters use telephone numbers as their “box of marbles.” If cell-phone numbers aren’t listed, then they can’t be put in the box of marbles. This only becomes a problem if people without landlines are largely different from those with landlines and if this number becomes large enough to affect the sample. I am personally of the opinion that we have not reached that point yet.

thank you michael. One very important question. How do they pick ” likely” voters? More and more people I talk to were very apathetic, now they are becoming more involved bc they are fed up with what’s going on.

Each pollster has his or her own model for deciding who is a “likely” voter. However, most include a combination of the answers to the following questions:

1. Did you vote in the previous election?
2. How interested are in you the current election?
3. Do you plan to vote in the upcoming election?

Voters who respond, “Yes, Very, and Yes,” respectively, are very likely to actually go out and vote. If a pollster calls one of the people you’ve talked to, who used to not care, but are fired up now, they might respond, “No, Very, and Yes,” respectively, and would then probably, depending on the pollster, get classified as a Likely Voter.