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View Diary: How whites really voted in 2008 (98 comments)

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  •  Listen, exit polls are polls of people after they (0+ / 0-)

    already voted. So, you don't have to wonder if they really will vote...

    And you do not appear to understand the formula used to generate margin of error either.
    1/ square root of n.  

    And you can weight around sampling bias.  

    There's also bias in who will answer the telephone as so many of us have caller id and others don't have landlines.

    I agree with Kos.

    •  There is actually a difference between (0+ / 0-)

      the margin of error of a random sample, as in a poll, and a non-random sample, as an exit poll.
      Dana, of course a poll has a chance to be perfect, because most people can be included in the poll. Pew even uses cellphones, as far as I know.
      But in the Exit Poll, something like 95% of voters had NO CHANCE to participate because there was no exit pollster near their precinct. 2,200 respondants, probably from less than 500 precincts, while there are about 20,000 precincts in California.

      The exit poll is a (more-or-less, even here apply caveats, like- did the pollsters do interviews the whole voting time?) random sample of those 500 precincts, and the margin of errors applies for those. And I think that Edison&Mitovsky tries to choose the precincts as such that they are as representative of the State of California as possible (some rural areas, more urban areas, some GOP leaning areas, some Dem-leaning areas etc.pp)... but that is impossible when you don't do a random telephone poll.

      math4barack- I know the formula for MoE, and I know what an exit poll is. But the Margin of Error is used for expressing the confidence interval of RANDOM sampling errors. The sampling errors of the exit poll are not random, however, they get that errors because their sampling poll includes just like 5% of the voters. Not their sample- the pool they draw the sample from.

      Of course, telephone polls have their own problems- caller ID, likely voter model errors (however not cellphones, because Pew polls those)- but they diminish when you look at the problems of the exit poll.

      •  . (0+ / 0-)

        however, they get that errors because their sampling poll includes just like 5% of the voters.

        Sorry, I mean the sampling pool, of course.

      •  the precincts arn't random though (0+ / 0-)

        The precincts for exit polling are very carfully selected to reflect the state as a whole.  Precincts that have similar results to the state as a whole, precints that can predict turnout for both republicans and democrats.  It's a bit of a science, and is why they can use a small sample to estimate results.  I once say someone estimate, within a couple percentage points, the results from a city election with only only one precinct results.

        Also, a  sample size of 2500 isn't small for the state of CA.  Many national polls use a sample size of 3000.

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