Probability

Question 1

General Rules (probability)

Answer 1

If an event E is certain to occur then P(E) = 1. If event is certain not to occur then P(E) = 0. If an event is possible but not certain then 0 < P(E) < 1. Sum of probabilities of all possible outcomes is 1.

Question 2

Probability that event E will occur

Answer 2

P(E) = (# of outcomes where E occurs)/(total # of outcomes)

Question 3

Probability that event E will not occur

Answer 3

equal to 1 - P(E), the complement of an event

Question 4

Mutually exclusive events

Answer 4

Two events are mutually exclusive if they can’t happen together: P (E and F) = 0

Question 5

Probability of events E and F (if independent events)

Answer 5

P(E and F) = P(E) x P(F)

Question 6

Probability of events E or F (E happens, F happens, or both E and F happen)

Answer 6

P(E or F) = P(E) + P(F) - P(E and F)

Question 7

Probability of events E and F (if dependent events)

Answer 7

P(E and F) = P(E) x P(F | E) where P(F | E) is the probability that F occurs given that E occurs Ex. the probability of drawing a heart, assuming you already drew a spade