Year 11 Probability

Question 1

P(Event)

Answer 1

P(Event) = matching outcomes / total possible outcomes
Example:
P(Tails) = 1 / 2
P(rolling a 6) = 1 / 6

Question 2

Theoretical probability

Answer 2

When we know the underlying probability of an event

Question 3

Experimental probability

Answer 3

Probability based on observing counts
AKA relative frequency

Question 4

A spinner has letters ABC on it.
It is spun 50 times and A comes up 12 times
Find experimental probability for P(A)

Answer 4

12 / 50 = 0.24

Question 5

Examples of sample spaces

Answer 5

Throwing a 6
Throwing an odd number
Tossing a heads
Picking a red counter

Question 6

Sample space

Answer 6

Set of all outcomes
Ɛ symbol represents the sample space
Ɛ CARD TO BE CONTINUED

Question 7

A fair coin is thrown and lands on heads twice. What is the probability of a head on the third throw?

Answer 7

1 / 2 because each throw is an independent event

Question 8

Given that all three balls drawn are the same colour, find the probability that they are all red

Answer 8

P(all red | all the same colour)
= P(all red) / P(all 3 same colour)
= P(R, R, R) / P(R, R, R) + P(Y, Y, Y)

Question 9

Mutually exclusive events

Answer 9

Events that cannot happen at the same time
P(A or B) = P(A) + P(B)

Question 10

Independent events

Answer 10

The outcome of an event does not affect the outcome of the next event
P(A and B) = P(A) x P(B)

Question 11

And and or in probability

Answer 11

A and B = A x B
A or B = A + B

Question 12

How to fill Venn diagrams that have 3 circles

Answer 12

Start the section that has the most overlaps
Then next sections that have the most overlaps, MAKE SURE TO SUBTRACT THE MIDDLE OVERLAP NUMBER FROM THESE NUMBERS. If the number to subtract is too big don’t subtract it
Continue the process