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View Diary: The Meta-Analysis Of State Polls is back! (w/poll) (31 comments)

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  •  really?... (0+ / 0-)

    Computers are quite fast and performing millions or even hundreds of millions of Monte Carlo draws from a simple distribution is relatively trivial -- waiting a few minutes for a results instead of a few seconds.  In addition, you still haven't addressed the point that the results are NOT exact or even very precise in the usual meaning of these words if there are many "toss-up" states.  The fundamental uncertainty in the state polls still dominates the overall uncertainty.  

    •  "Trivial" - but wrong (0+ / 0-)

      Yes, computers can calculate that quickly. But you are missing the point. It is inexact to carry out such simulations, much the same way that one would not make a serious calculation of pi by repeatedly measuring the circumferences and diameters of circular objects.

      You seem to have an interest in statistical methods. Read the writeup on my site. Then, if you still have questions, please write to me at sswang at princeton dot edu.

      In the meantime, here is a direct example of what I am talking about.

      Here is the result of 10,000 simulations done yesterday at fivethirtyeight.com:

      and here is the exact distribution of probabilities of all >2 quadrillion outcomes, calculated from the state probabilities posted there:

      Assuming that the EV estimate posted on that site is based on the simulations, the value posted there today is currently off by 5 EV. Considering the care with which the state probabilities are calculated, this is a major oversight.

      •  I understand (0+ / 0-)

        I understand your approach and I also understand that 10000 simulations might be less than ideal.  A million would probably be better.  I just think that words like exact and precise don't apply that much to meta-analysis of polling data three months before the election.  

        BTW, I think your formula is pretty cool and Poblano should use it.  But it's his method for weighting polls and imputing results for thinly polled states through the demographic regressions that seem to make his projections better than the simple meta-polls.  That piece of the analysis is even more important than whether he does 10,000 simulations, or 1 million, or realizes that there's an easier way forward to get at the distribution (like your formula).

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