
Ask HN: Political Polling Methodology? - forkandwait
Is there anyone here who can describe in some mathematical detail how an election forecast is calculated?<p>Obviously, I wonder why the latest presidential race forecasts were so consistently wrong,  but I am curious in general too.<p>I imagine for every response (&quot;yes, I will vote for Trump&quot;) there are weights for  how representative is that response, how likely,  and what is the associated turnout. But I am sure it is more complex.
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pcunite
>> why the race forecasts were so wrong

Because America is not just New York, Silicon Valley, and Hollywood. The
media, pollers, and forecasters shared a narrative that they wanted to be
true, not one that was actually grounded in _investigated_ reality. We should
all take from this experience to seek for truth, the way it is, not the way we
wished it could be. Save that for opinion polling.

Anecdotal:

The media was telling me _no one in their right mind_ could side with Trump.
Okay. I was watching both candidates online and there would be like 70,000
watching Trump and maybe 3,000 watching Hillary. Personalities like Lady Gaga
don't equate to 60,000 people.

Trump had more twitter followers, more FaceBook likes, and more people at his
rallies. All the data was there. It is just that the media did not want to
report that. And finding out the reasoning behind that ... well, that would be
an interesting conversation.

~~~
blairbeckwith
I think that – sadly – a lot of people assumed that the majority of people
watching the rallies and following on social media were there for the
entertainment value. I think some were, but it seems like most were there
sincerely.

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zzzcpan
> Obviously, I wonder why the latest presidential race forecasts were so
> consistently wrong

I think it's rather obvious, some people didn't want to participate in the
polls, likely out of shame for their candidate, fear of being shamed for their
choice in front of their peers, etc.

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dumbmatter
[http://fivethirtyeight.com/features/a-users-guide-to-
fivethi...](http://fivethirtyeight.com/features/a-users-guide-to-
fivethirtyeights-2016-general-election-forecast/) is a decent overview of the
most popular forecast. There's plenty of other relevant content on that site,
too.

~~~
matt_s
That group was featured on ABC news coverage last night in the US. They
predicted Clinton would win 70% to 20% early in the evening.

I didn't read what they said about their process but they were completely off
too.

~~~
dragonwriter
> They predicted Clinton would win 70% to 20% early in the evening.

No, they predicted about a 70%:30% chance of Clinton vs. Trump win, not a 70%
to 20% win by Clinton.

> I didn't read what they said about their process but they were completely
> off too.

It wasn't so much that they were completely off as that some people mistake a
claim of probability > 50% with a claim of certainty.

Sure, the most-likely winner map was wrong in a number of states, but the
reason 538 had a 30% chance of Trump winning rather than much lower chances
given by other models was that 538 takes into account the fact that deviations
in results from polling in different states tend to be correlated rather than
independent.

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ryanmccullagh
You'll most likely find that methods are proprietary. Some companies are in
this space. For example, a company I was just rejected from claimed they have
a monopoly on polling. A quick search could reveal who this company is. Hint:
Eric Schmidt is on the board.

