Ms. Garcia Math
The probability of event A is the number of ways event A can occur divided by the total number of possible outcomes.
Events mutually exclusive
Two events are mutually exclusive if, when one event occurs, the other cannot, and vice versa.
Example: Tossing a coin once. Can result in either heads or tails, but not both.
The complement of any event A is the event [not A]
Example: Turning a Head and Turning a Tail are complementary events.
P(A) + P(Not A) = 1
The probabilities of two complementary events add up to 1 .
P(Head) + P(Tail) =
½ + ½ = 1
An event that cannot be decomposed is called a simple event.
rolling a 6
on a die has the probability of 1/6
Are the combination of multiple simple events
rolling an even number
on a die has the probability of 3/6
= P(2 or 4 or 6) = 3/6 =
If two events have no outcomes in common, the
probability that one or the other occurs
is the sum of their individual probabilities.
P(2 or 4 or 6)
= 1/6 + 1/6 + 1/6 =