Probability Terminology

If A and B are mutually exclusive events, then:

• Either A or B must happen

• Both A and B must happen

• If A happens, so does B

• A and B can't both happen

If A and B are mutually exhaustive events, then:

• A only happens if B happens too

• A and B can't both happen

• If B doesn't happen, A must happen

• A and B do not affect one another

If A and B are independent events, then:

• The probability of B is affected by whether A happens

• A and B cannot both happen

• The probability of A is lower if B happens

• The probability of A is not affected by whether B happens

A' means the complement of A. Which of these is never true?

• P(A) + P(A') = 1

• P(A∪A') = 1

• P(A) ÷ P(A') = 1

• P(A∩A') = 1

In general, the probability of A and B happening is:

• The same as the probability of A

• Lower than the probability of A

• More than the probability of A

In general, the probability of A or B happening is:

• The same as the probability of A

• Lower than the probability of A

• Higher than the probability of A

The probability of A given B means:

• How likely it is that A and B both happen

• How likely it is that A happens when we know B happens

• How likely it is that B happens when we know A happens

• How likely it is that A happens, but B does not

P(A∪B) = P(A) + P(B) is true when:

• A and B are independent events

• A and B are mutually exclusive events

• A and B are mutually exhaustive events

• P(A) + P(B) ≤ 1

P(A∩B) = P(A) × P(B) is true when:

• A and B are independent events

• A and B are mutually exclusive events

• A and B are mutually exhaustive events

• P(A) × P(B) ≤ 1

P(A|B) = P(A) is only true when:

• A and B are independent events

• A and B are mutually exclusive events

• A and B are mutually exhaustive events

• P(B) = 1