Class 2: Probabilities

Question 1

n/N

Number of ways this event can occur divided by total number of events

Answer 1

Probability of an event

Question 2

1 - P(E)

Events are equally likely and not mutually exclusive

Answer 2

Probability of not that event

Question 3

P(A)P(B)

Probability of occurrence of two independent events, A and B, is equal to P of each event

Answer 3

P(A and B)

Question 4

P(A) + P(B) - P(A and B)

The probability of each minus the probability of both

Answer 4

P(A or B)

Question 5

EA can occur n1 ways, EB can occur in n2 ways, EAB can occur in (n1)(n2) ways

Answer 5

Number of ways

Question 6

(n)(n-1)(n-2)…

Number of ways n objects can be ARRANGED

Answer 6

N! (N factorial)

Question 7

If n = r, then

Answer 7

0! = 1

Question 8

n! / (n-r)!

Selection of r objects from a group of n objects, when the order of selection matters

Answer 8

P(n, r)

Permutations

Question 9

n! / r!(n-r)!

Selection of r objects from a group of n objects when the order does not matter

Answer 9

C(n, r)

Combinations