Consider a man who claims to be able to locate hidden sources of water by use of a divining rod. To test his claim, he is presented with 10 covered cans, 1 at a time; he must decide, by means of his divining rod, whether each can contains water. What is the probability that the diviner will make at least 7 correct decisions just by chance? Do you think that the test described in this exercise is fairer than the test described in exercise 2.14 of Chapter 2? Will it make a difference if the diviner knows how many of the' cans actually contain water?