Probability

Question 1

How to find P(A|B)

Answer 1

P(AnB)
———
P(B)

Question 2

Mutually exclusive

Answer 2

P(AnB) = 0

Question 3

P(AuB)

Answer 3

P(A) + P(B) - P(AnB)

Question 4

Independent conditions

Answer 4

P(AnB) = P(A) X P(B)

P(A|B) = P(A)

Question 5

P(B|A) if you know P(A), P(B) and P(A|B)

Answer 5

P(A|B) X P(B)
——————
P(A)

Question 6

P(A)’

Answer 6

1.00 - P(A)

Question 7

How many different possie teams of x people can be made from y people.
y > x

Answer 7

yCx

y! / ( (y-x)! (x)! )

Question 8

How many ways can y things be ordered if each thing is used onced / not repeated.

Answer 8

y!

Question 9

How many ways can y things be ordered if each thing is used onced / not repeated and x things have to be together

Answer 9

(y+1-x)! X (x)!

Question 10

When to use choose

Answer 10

If the event isn’t at a set time

20 tackles find the probability 2 miss
20C2 X P(miss)^2 X P(tackle)^18

Question 11

WIN = 0.6
LOSE = 0.4

Find the probability WIN happens for the xth time on the yth try

Answer 11

(y-1)C(x-1) X (0.6)^x X (0.4)^y-x

WIN third time on seventh try
6C2 X (0.6)^3 X (0.4)^4