1. ©G Dear 2009 – Not to be sold/Free to use
Relative
Frequency
General Mathematics
Preliminary
Relative Frequency
Stage 6 - Year 11
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©G Dear 2009 – Not to be sold/Free to use

2. Complementary Events (1/3)
Definition
The Complementary Event is the event that describes all other possible events.
Example:
E = {winning a race}
Complement of E = {NOT winning a race}
Complement of E = {loosing a race}
Wrong

3. Complementary Events (2/3)
The Sum of the Probabilities of an Event and its Complement add to ‘1’.
Example: For a dice 2 6 1 3
P(>4) = = 4 6 2 3
P( Complement >4) =
P(≤4) = = 1 3 2 3
P(>4) +
P( Complement >4) = +
= 1

4. Complementary Events (3/3)
To find the Probability of an Event, subtract the probability of its Complement from ‘1’.
Example: For a standard pack of cards
P(Spot Card) = 1
- P( Not Spot Card) 12 52 -
= 1 10 13 =