I'd heard the ones about cancer before, but I hadn't heard this:
Asked in an experiment to guess how many abortions occur in the US for every million live births, students gave a wide range of answers. At the middle of the range was an estimate of 5,000. That figure is so far from the correct answer - 335,000 - that, in the words of the physicist Wolfgang Pauli, it is "not even wrong."
But I used to give a quiz to one of my classes with similar questions. For example: how many battle deaths did the U.S. suffer in the Vietnam War?
I had quite a few college students--I forget the exact percentage, but I think it was 20 percent or so--answer more than 500,000.
And they each had exactly as many votes as I do.