Two events are complementary (i.e., they are complements) if:
A)the sum of their probabilities equals one.
B)they are disjoint and their probabilities sum to one.
C)the joint probability of the two events equals one.
D)they are independent events with equal probabilities.

Question

Quizplus · Accepted Answer

Complementary events are those which together cover the entire sample space and have no common outcome. Hence, they are disjoint and their probabilities sum to one. Option (A) is true for any two mutually exclusive events, not necessarily complementary events. Option (C) is true only for certain specific cases, not generally for complementary events. Option (D) is also not true in general for complementary events.

Two Events Are Complementary (I