A drawing pin was dropped 400 times and it landed point up on 260 of those drops. On the evidence of this experiment, what is the probability that the next drop leaves it point DOWN?

The pin landed point down 400 − 260 = 140 times, so the experimental probability is 140/400 = 7/20. Answering 13/20 gives the probability of point UP, 260/400. The value 1/2 assumes the two ways of landing are equally likely, which the record plainly contradicts — a drawing pin is not a coin, and only a long run of trials can supply its probability. Comparing the two counts with each other, 140 : 260, gives 7/13, which is an odds ratio rather than a probability.