According to the National Weather Service there is a 20% chance it might rain here tonight. Do you know that means? A lot of people don’t.
A recent study of college students by the University of Washington in Seattle shows that many completely misunderstand the notion of “probability-of-precipitation.” Some imagine that if there is a 20% chance of rain, that means that 20% of their town will get rain and 80% won’t. Others understand it to mean that it will rain 20% of the day. Can we be that dumb?
To find out, I walked out among my neighbors and townsfolk and asked them to explain the meaning of today’s forecast. Here are just some of the answers I received:
“It means that there is a 20% chance that God is going to flood the earth tonight.”
“It means that 20% of the people want it to rain tonight.”
“It means that the weather girl only looked at 20% of the map.”
“It means that only 20% of the town will get wet.”
“It means that you are a dumb Jew-bastard who has yet to accept Jesus Christ as his Lord and Savior and who has a 100% chance of going to Hell.”
OK, I made the last one up. Well, no, I didn’t make it up exactly, I simply transposed it from another conversation to this conversation about weather. The prior conversation was about whether or not I was going to Hell, so you can see how easy it was for me to make the leap from one conversation to another. Homonyms are our friends.
The Seattle study found that if the weather forecaster added the probability of no rain along with the probability of rain, people understood things better. So if you say to someone, there is a 20% chance that it will rain tonight and an 80% chance that it won’t, chances are the person will understand what you are saying. So I tried that and got this:
“Do I have a choice? If I do, I’ll take the 20% ‘cause we need the rain. If I don’t I’ll take the 80%.”
Now you may be as confused about the weather as the people in my survey, so let me make it simple. On any given day there is always a 50/50 chance it will rain. It will either rain or it won’t rain. On or off, that’s all there is to it. It will rain or it won’t. It will snow or it won’t. We’ll be hit by an asteroid or we won’t. Jesus will return today or he won’t. It is always 50/50. That’s why I buy lottery tickets: I always have a one in two chance of winning whether or not it raiins.