Rules Of Probability

Question 1

All probabilities are proportions
True or false?

Answer 1

True

Question 2

All non overlapping probabilities for a random process must sum to 1
True or false

Answer 2

True

Question 3

The probability of an event not occurring is equal to 1 - the probability that it does occur

Answer 3

Complement rule

Question 4

[probability of desired outcomes] + [probability of not desired outcomes] = 1

• key words not and atleast 1*

Answer 4

Complement rule

Question 5

The probability that A or B (or both) occur is
P(a) + P(b) - P( a and b)
* key word or*

Answer 5

Addition rule

Question 6

For 2 independent events A&B, the probability that both occur is P(A and B) = P(A) x P(B)
* key word and*

Answer 6

Multiplication rule

Question 7

When can you use multiplication rule?

Answer 7

If both variables are independent; must use rule to check if independent.

Question 8

Probability of an event when another event is guaranteed to have occurred

P(A given B)= P(A&B)/ P(B)

Answer 8

Conditional probability