I am sorely puzzled by the percentages that weather forecasters give to the chance of precipitation.
They say, for instance, that there is a 30% chance of rain in Milford on Monday.
What does this mean? There is a 30% chance that a single drop of rain will fall somewhere within the borders of Milford on Monday? That 30% of the day it will be raining and 70% of the day it will not? That it is likely to rain in 30% of the area of Milford, but the other 70% will be dry?
Not a single one of the above formulations of a "30% chance of rain" strikes me as plausible. Yet if none of those are correct, just what does it mean to say that there is a 30% chance of rain in Milford on Monday?
To add to my confusion, when the Weather Channel predicts a 30% chance of rain, for that day they show a rain icon along with the prediction. But doesn't this prediction mean that there is a 70% chance that it won't rain? Why, on a day when the odds are 7-to-3 against there being rain, is a rain icon the correct choice for symbolizing what will be going on that day?