People Don’t Get Probability

Whether it’s about elections or hurricane predictions, neither the media nor the public understand probability. I suspect this is because we are evolutionarily programmed to look for certainty. Certainty leads to decisive action. It is sometimes said in military circles that a bad decision is often better than no decision. But it’s easy to be decisively wrong.

For example, if you looked at the actual data about Hurricane Irma, and looked at the predicted range of possibilities (you know, either the cone or those circles around the predicted center), the prediction process went quite well. As reported in the media and as “understood” by many in the public, not so much.

Thus I read with great pleasure Nate Silver’s article today at FiveThirtyEight.com (one of my favorite sites), The Media Has A Probability Problem. There were those who criticized Silver for his data analysis in the 2016 election where he was giving a greater probability of a Trump victory than anyone else. Not predicting a Trump victory, but giving it a higher probability. There were those who were rating Clinton’s chances in the high 90s. Following the election there are those who see Silver as wrong, along with the rest. But that’s a probability. A 30% chance is hardly a prediction that something won’t happen. If you understand probability, that is.

Most don’t. Or they understand it in their heads, but don’t feel it. Here’s a summary from Nate Silver:

Probably the most important problem with 2016 coverage was confirmation bias — coupled with what you might call good old-fashioned liberal media bias. Journalists just didn’t believe that someone like Trump could become president, running a populist and at times also nationalist, racist and misogynistic campaign in a country that had twice elected Obama and whose demographics supposedly favored Democrats. So they cherry-picked their way through the data to support their belief, ignoring evidence — such as Clinton’s poor standing in the Midwest — that didn’t fit the narrative.

Now don’t take this as supporting President Trump’s cherry-picking of polls and numbers. That’s just another, less nuanced form of confirmation bias, or more likely simple carelessness with and disregard for facts.

Further, if we are going to blame the media for problems, we need to watch where we go instead. Many blame the media for very real problems of bias, stupidity, and deception, only to turn to even less reliable sources which they believe implicitly. One advantage I’ve found with reasonably good media reports is this: If you read beyond the headline, and check the references, you can almost always find what you need to double check and correct the news story. For example, most news organizations provide links to the actual poll data and analysis.

So if you want good information, follow the chain back to the source. Don’t just find something more agreeable and believe that. There are perfectly good ways to analyze data and avoid errors. None of us is perfect, but we can and should be better. Much better.