Here's something: The National Oceanic and Atmospheric Administration's National Weather Service employs a social scientist whose job it is to interpret how people interpret her employer's forecasts. In other words: What do people think "20 percent chance of rain" actually means?
Well, as part of of a week-long series about risk and probabilities, NPR ran a piece centered around this question ... and then they had to run a follow-up piece because enough readers felt that "a concise explanation of 'a 20 percent chance of rain' was missing from" from the original story. The hopefully-concise-enough explanation given by a meteorologist in the follow-up story:
It simply means for any locations for which the 20 percent chance of rain applies, measurable rain (more than a trace) would be expected to fall in two of every 10 weather situations like it.
One day we'll all tell our kids about the confounding randomness of this clear, nourishing, celestial nectar that once fell from the sky. —Ryan O'Hanlon