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st: Re: poll of polls


From   "Eric Uslaner" <euslaner@gvpt.umd.edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: poll of polls
Date   Wed, 23 Jun 2010 08:15:47 -0400

Richard Ohrvall wrote:

> I am sorry if this is a bit too unspecific, but I am currently looking
> into what is usually called "poll of polls", i.e. techniques to take
> estimates from different opinion polls and estimating time series. I
> know, it is outside of established statistical theory, but I am
> playing around with political opinion polls to look at different
> methods to achieve time series. Some of the issues are a) how to
> handle "house effects", i.e. that different pollsters systematically
> diverge from others, b) how to smooth the data over time, e.g. some
> sort of moving average. So, my questions are 1) if any of you have
> seen anything done on this using Stata? 2) Do you have any
> ideas/suggestions about the best way to tackle this (e.g. if -lowess-
> is a path worth exploring)?

[...]

You need to be very careful in averaging polls.  I know that pollster.com does it and I have a lot of respect for the folks there (and know Charles Franklin).  But if you look at Nate Silver's www.fivethirtyeight.com , you will see that he has an analysis of the accuracy of various pollsters and he finds that IVR polls (AKA robopolls) generally have far less accuracy.  They do not follow standard AAPOR polling practices and thus they are not random samples in the true sense (so that their sampling errors are not accurate).  Simply averaging all polls is akin to measuring the weight of apples, peaches, and watermelon and saying that the mean is the average weight of fruit.

Ric Uslaner



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