Probability

How to approach permutations questions

□ x □ x □ …

What is a permutation?

an arrangement of objects or numbers in a definite order

What is a combination?

an arrangement of objects or numbers in any order

How to approach a combinations question?

nCr

What is the significance of the word and?

always multiply

What is the significance of the word or?

always add

How to expression probability as a fraction?

outcome/number of possible outcomes

What does mutually exclusive mean?

can’t happen at the same time, one or the other

What is the formula to show an event is mutually exclusive?

P(A U B) = P(A) + P(B) 

What does independent mean?

the outcome of one event does not effect the outcome of the other, but they can happen at the same time

What is the formula to show an event is independent?

P(A ∩ B) = P(A) x P(B) 

What does conditional mean?

P(A I B) = P(A ∩ B)/P(B)

The probability of A given that B has occurred is equal to outcomes where both A and B happen/ the outcomes where B happens