Probability

(A n B)

where both A and B occur ( intersection)

(A u B)

where A or B or both occur

A'

Not A

(A n B)'

Not the intersection

(A u B)'

Not A and not B

B c A

B is a subset of A

How to find the probability that A doesn't occur (A')

1- P(A)

how to find the probability of equally likely outcomes

number of outcomes / total number of outcomes

P= r/N

Probability of non equally likely outcomes

Numbers of times the event occurs / number of trials ( total amount)

P=r(A)/N

What is P(AnB) in mutually exclusive events

0

What is the addition law for mutually exclusive events?

P(A u B)= P(A) + P(B)

- can only be used for mutually exclusive

What is the generalised addition law?

P(A U B ) = P(A) + P(B) - P( A n B)

When can the generalised addition law be used?

Whenever

- doesn't matter whether its mutually exclusive or independent

- used for both

Multiplication law for independent events

P(A n B) = P(A) x P(B)

How do you calculate the probability of exactly 1 event?

P(A U B)- P(A n B)

P(AUB’)

Everything in A and everything not in B

\
1- (P(B)- P(AnB))

How to find P(AUB) when given P(A’nB’)

1- P(A’nB’)

P(A’n B’)

Just the outside

\
Not A B and intersection