Probability Revision Quiz

“I roll a normal dice and get a 7” This event is:

Impossiblea)b)c)d)

Unlikely

Even Chance

Certain L3

“A fair sided dice will land on an odd number” This event is:

Impossiblea)b)c)d)

Unlikely

Even Chance

Certain L4

“It can either rain or not rain. So the probability it rains is ½”. True or False?

True False

L5

I have 10 sweets in a bag. 3 chocolates, 2 toffees and 5 fudges. The probability I pick a

toffee at random is:

510a)

b)

c) d)

210

28

L5

The letters from the word NECCESSITY are put on cards and turned over. I pick one at random.

What is the probability that I pick a vowel?

I spin the following spinner

a) What is the probability that the spinner lands on the pink part?

b) What is the probability that the spinner lands on a blue part or a green part?

b) What is the probability that the spinner lands on the red part or the green part or the yellow part or the blue part?

What is PROBABILITY?The chance of some particular thing

happening (EVENT)

Examples

The probability of getting an A in my Math exam

The probability that it rains tomorrow

The probability that I win the lottery today

Possible outcome

s

Two types of Probability

The CALCULATION of something happening

In Theoretical Probability we

PREDICT WHAT SHOULD BE

What ACTUALLY happens

In Experimental Probability we

FIND OUT WHAT IS

THEORETICAL

EXPERIMENTAL

Why can the results of experimental probability be different to theoretical probability calculations?No one can tell exactly what is going to happen in the future, what happened in the past can help predict the future which is what we do in theoretical probability BUT we can never know for sure what actually happens which is what we find out in experimental probability

P(EVENT) P(Event A) = The number of ways A can happen

The total number of possible ways

• P(Impossible event) =

• P(Certain event) =

• P(any other event) =

• P(event A or event B) =

• The sum of the probabilities of all possible outcomes =

0

1

Between 0 and 1P(event A) + P(event B)

1

The Probability Line

ALWAYS Between 0 and 1 : FRACTION , DECIMAL (or

PERCENTAGE)

Equally Likely

The Probability of an event NOT Happening

• I have a box of 7 different CDs, 3 are music CDs.

What is the probability of NOT picking a music CD?

• In how many ways can I NOT pick a music DVD? 4 ways4/7

Probability of an event NOT happening

Question: What is the relationship between

P(Music CD) = 3/7 and P(NOT Music CD) = 4/7 ?

P(NOT Music CD) = 7/7 – 3/7 = 4/7 = 1 – P(Music CD)

IN GENERALThe probability of an event NOT happening is found by

deducting from 1 the probability of that event happening! (finding the COMPLEMENT!)

Probability of an event not happening

Probability of an event NOT happening:

1 – Probability of EVENT happening

Worksheet