If two events are complementary, then we know that:
A)the sum of their probabilities is one.
B)the joint probability of the two events is one.
C)their intersection has a nonzero probability.
D)they are independent events.

Question

Quizplus · Accepted Answer

Complementary events are events that are opposite to one another, in the sense that one event is the event that the other event does not occur. For example, the event of getting heads on a coin flip is complementary to the event of getting tails. Therefore, if one event has a probability of p, then the complementary event has a probability of 1 - p. Since the sum of the probabilities of complementary events must equal one, the best choice is A, the sum of their probabilities is one.

If Two Events Are Complementary, Then We Know That