Parents learn tricks that are helpful in raising children and in preserving the sanity of all concerned. When a baby is crying, just changing diapers will stop crying 25 percent of the time. Picking the baby up and walking stops crying 40 percent of the time. Suppose a (desperate?) parent did both. Which outcome (percent) would indicate that the effect of the two tricks is independent, that they do not interact?
A) 25
B) 40
C) 65
D) 75

Question

Quizplus · Accepted Answer

If the two tricks are independent, the probability of stopping the crying by doing both should be the sum of the individual probabilities minus the probability of both occurring together: 25% + 40% - (25% * 40%) = 65%.

Parents Learn Tricks That Are Helpful in Raising Children and in Preserving