innumeracy

It was a blustery day on the Santa Barbara-Ventura coast this morning. When I opened the car door to get out at the harbor, the wind blew the handle right out of my hand.

No surprise, then, that the day's boat trips out to the Channel Islands were cancelled. This was of concern to me, as I was booked on one of them.

The phone message had said to call the agency's office back to rebook or obtain a refund, but I figured that since I was right there anyway, I might as well go in in person.

The first thing I asked when considering a rebooking was, How often do trips get cancelled? "Fairly frequently in the winter and spring because of storms and wind," they said. "It's fifty-fifty." That bad? I exclaimed. How about in the summer, then?

"That's fifty-fifty," they said.

Wait a minute, I said. Didn't you imply that spring trips were more likely to be cancelled than summer ones? Then how can they both be 50-50?

We went around on that a bit, and then I realized that when they said "fifty-fifty" they weren't giving odds. "It's like flipping a coin, fifty-fifty," they said, from context clearly taking "fifty-fifty" not as numbers but as some kind of rote phrase meaning "You can't predict in advance what's going to happen."

Well, I knew that. I wasn't asking for the prospects of a particular trip two weeks or two months out. I just wanted to know what kind of odds I was facing that I'd drive five hours and pay for a hotel room (so that I could be there at 8:30 AM for the boat trip) again only to face another cancellation.

So I told them that when you flip a coin, half the time it's heads and half the time it's tails. If heads means 'go' and tails means 'cancel,' then you're cancelling half the trips. Sorry, but that's what 'fifty-fifty' means.

Then I went concrete. How many trips have you had scheduled in April so far, and how many have been cancelled? They went and looked it up. The answer came to about 5%. That's much better odds, so I rescheduled.

But that's innumeracy for you. Using the phrase "fifty-fifty" to indicate the unpredictability of an event - which was not in response to the question I was asking - when the actual odds are about 5%.

Have you ever encountered this particular form of malcommunication?