Probability

Question 1

Probability of an event

Answer 1

Probability= number of possible outcomes/ total number of possible outcomes

Question 2

Probability of an event not happening

Answer 2

P(A’)= 1-P(A)

Question 3

Probability of A or B

Answer 3

P(AUB)= P(A)+P(B)
A and B all shaded in venn diagram (including intersection)

Question 4

Probability of A and B

Answer 4

P(A∩B)= P(A) x P(B)
Shading of intersection

Question 5

Mutually exclusive events

Answer 5

P(AUB)= P(A) + P(B)

Question 6

Not mutually exclusive events

Answer 6

P(AUB)= P(A)+P(B)- P(A∩B)

Question 7

Probability distribution

Answer 7

P(X=x) - “the probability that the outcome of the random variable X was the specific outcome x”
p(x) is also the same thing

Question 8

How else can probability outcomes be displayed

Answer 8

As a function: p(x)= {0.1x, x=1,2,3,4
{0,
Or as a table with x on top and P(X=x) at the bottom

Question 9

Advantages of functional and table form

Answer 9

Functional:
+ Can have an expression based on the outcome
+ More compact
Table:
+ Probability for each outcome is more explicit

Question 10

Expected value of X formula

Answer 10

E(X)= total of (x(p(x))
Represents mean outcome if experiment was done several times