The importance of definitions: chance of rain

Tomorrow’s weather forecast for Carlisle, PA, is: Windy with showers. High 58F. Winds SW at 20 to 30 mph. Chance of rain 40%. First of all, 58 degrees on December 28? Sweet! But what does “chance of rain 40%” mean? Does it mean that there is a 40% chance that it will rain at my…

How did the pollsters do?

A few weeks ago I wrote about Fivethirtyeight.com, the website run by Nate Silver which made political predictions based on aggregating existing polls. You may want to check out a blog post by Carl Bialik, The Numbers Guy at the Wall Street Journal, in which he looks the accuracy of Nate Silver’s and other pollsters’ predictions. Here’s…