4.7 For each of the following situations, discuss whether the term probability seems to be used correctly and, if so, how such a probability might have been determined.

a A physician prescribes a medication for an infection but says that there is a probability of 0.2 that it will cause an upset stomach.

b An engineer who has worked on the development of a robot says that it should work correctly for at least 1,000 hours with probability 0.99.

c A friend says that the probability of extraterrestrial life is 0.1.