Let’s Talk About Polling

Over the past couple weeks many polls were showing Hillary Clinton had a very distinct lead, but as Election Day nears, it the margin has closed considerably.

According to fivethirtyeight the largest gap between the two candidates was just before the 3rd debate with Hillary having an 88.6% chance of winning and Donald Trump having an 11.9% chance of wining. As of right now November 4th 11:28 pm, the prediction is that Clinton has a 64.5% chance of winning and Trump has a 35.4% chance.

On the other hand, from Oct 21st to October 25th, The Upshot had Clinton at a 93% chance of winning and Trump at a 7% chance of winning. Right now, their prediction is that Clinton has an 85% chance of winning and Trump has a 15% chance.

So who do we believe? Both have Clinton in the lead but the margin by which she leads is drastically different. The way the chance of winning is calculated is by looking at what various polls are showing and giving each poll a different weight in the calculation. Fivethirtyeight, The Upshot, and others have to consider which polls may be biased and which are more balanced.

For example, Rasmussen is historically a right leaning poll, whereas CBS News/NY Times and ABC/Wash Post Tracking tend to be more balanced. Thus, fivethirtyeight, The Upshot, etc. may not give Rasmussen a high weight in determining their election forecast percentages and will give a higher weight to other, more unbiased polls.

It is interesting to see the disparity between two, typically reliable election predictors. Nate Silver at fivethirtyeight predicted the 2008 presidential election to end with Obama getting 349 electoral votes and McCain getting 189 electoral votes. The actual results turned out to be Obama with 365 electoral votes and McCain with 173 electoral votes. As you can see Nate Silver’s projection was very accurate.

In the 2012 election, Nate Silver predicted that Obama would have 313 electoral votes and Mitt Romney would end up with 225 electoral votes. Obama ended up with 332 electoral votes and Romney with 206.

With that information in mind you may be inclined to think that Nate Silver’s prediction will be more on the mark. We’re just 3 days away from Election Day and will soon see which projection is most accurate.

Featured image courtesy of this article on Huffington Post. 

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