
The event A^{c}
("not A") is called the of event A
.
P(A)
+ P(A^{c})
sums to: .

If two events are independent, they do not: .
Whether a person is registered as a Democrat or whether that person is registered as a Republican are disjoint. Whether a randomly chosen person is registered as a Democrat and whether a second randomly chosen person is registered as a Republican are independent.

If two events A
and B
are independent, the probability that they both happen is equal to the of P(A)
and P(B)
.

Please answer question 4 to reveal this question.
If the events A
and B
are not independent, then the probability that they both happen equals P(B)
times: .
P(CD) is notation for the probability that the event C happens when you know that event D has occurred.

If two events are disjoint (i.e., mutually exclusive), they do not: .
Whether a person is registered as a Democrat or whether that person is registered as a Republican are disjoint. Whether a randomly chosen person is registered as a Democrat and whether a second randomly chosen person is registered as a Republican are independent.

The union of events A
or B
is often described using the words "A or B" (A ∪ B). This means that events A
or B
happened.

Please answer question 6 to reveal this question.
Assume events A
and B
are disjoint (i.e., mutually exclusive). To find the probability that at least one happens, P(A)
and P(B)
.

Please answer question 6 to reveal this question.
Now suppose events A
and B
do have overlap. To find P(A ∪ B)
, you take P(A)
+ P(B)
and then the probability of the overlap.