Relative frequency
100 teenagers were asked what their favourite type of movie was and the results were recorded in a frequency table.
The relative frequency is the FRACTION or PROPORTION of people in that particular category.
e.g. 15 out of the 100 teenagers liked action movies so the relative frequency of action movies is 15/100 = 0.15
Type of movie

Frequency

Relative frequency

Fraction

Decimal

Percentage

Action

15

15/100

0.15

15%

Comedy

35

35/100

0.35

35%

Drama

10

10/100

0.1

10%

Horror

40

40/100

0.4

40%

Total

100

1

1

100%

Based on these results it is more likely that the next person asked would like horror or comedy movies as they have the highest relative frequencies.
How likely an event is to happen can be predicted by its relative frequency.
Relative frequency

Likelihood of event happening

Above 90%

Very likely to happen

Above 50%

Likely to happen

Below 50%

Unlikely to happen

Below 10%

Very unlikely to happen

Probability
Example 1 
Answer 
When a die is tossed, what is the probability that a 5 or a 6 will face up?

Total six possible outcomes = {1, 2, 3, 4, 5, 6}
Required two outcomes= {5, 6}
P(E) = ^{2}⁄_{6} = ^{1}⁄_{3}

Example 2 
Answer 
A card is picked from a normal pack of 52.
What is the probability the card will be a heart?

There are 52 cards in a pack.
There are 13 hearts.
P(Heart) = 13/52 = 0.25

Probabilities will always be in the range from 0 to 1.e.g. 0 ≤ P(E) ≤ 1
If the probability of an event happening is 0, the event cannot occur.
If the probability of an event happening is 1, the event is certain to occur.
e.g. P(throwing a sixsided die and scoring a 7) = 0
P(throwing a sixsided die and scoring less than 7) = 1
See an activity involving probabilities when throwing two dice − .
(This activity was created by the Shodor Education Foundation)
