Election-polling math

[MicroBob]

This might have already been covered....apologies if this is the case. Just curious about the various presidential polls and the differences from one poll to another and one date to the next.

In one national poll I believe on CNN I thought I saw that there were 1100 or 1200 participants in the poll and their margin of error was +/- 4%.

Is this correct? With a national election of 100-150 million people or so (I'm guessing) you only need to poll 1200 individuals to be within 4%??? Is this with 95% confidence within 4% or 99%??

I know very very little about SD and probabilities etc. I just trust the experts' on the math (if I'm told I need a minimum of 300BB's then I go with that).

Without really knowing too much about the math involved, 1200 strikes me as a very small sample....but I seem to remember from one of my college courses that you really don't need as big a sample as you might think to accurately predict election results.

Also, remember that I only caught this graphic at a glance so I might have seen it incorrectly.

But I do suspect that smaller than necessary sample-sizes might be to blame for the various polls inconsistencies where Kerry leads in one poll by 2 points and Bush leads in another poll by 4 points, etc etc.

Additionally, I just find it hard to believe that there are really THAT many people out there who are changing their opinions of who they are going to vote for THAT much. I think that some of the day-after-debate fluctuations might have more to do with normal variance from less-than-adequate sample-size than it is a true reflection of where the country is leaning.

But, again, since I don't know much about the math I admit that this is little more than a hunch (and the evidence I see in the very different results from one poll to another)so I will defer to the super-duper knowledgeable folks of this forum.