**8.1- Introduction**

• calculate the probability of a single event as either a fraction or a

decimal

• understand that the probability of an event occurring = 1 – the

probability of the event not occurring

• understand relative frequency as an estimate of probability

• calculate the probability of simple combined events using possibility diagrams and tree diagrams where appropriate

**8.2- Probability experiments**

e.g. Use results of experiments with a spinner to estimate the probability of a given outcome

e.g. use probability to estimate from a population

**8.3- Theoretical probability**

e.g. P(blue) = 0.8, find P(not blue)

**8.4- Mutually Exclusive Events**

Mutually exclusive events are events that cannot happen simultaneously, or such that the occurrence of one means that the other cannot subsequently occur. if you throw a dice, only one face can be on top, so the events which described by the uppermost face are mutually exclusive.

The probabilities of mutually exclusive events can be added to find the overall probability of one of the events happening, so that if A and B are mutually exclusive events, then

P(A∪B) =P(A)+P(b)

In possibility diagrams outcomes will be represented by points on a grid and in tree diagrams outcomes will be written at the end of branches and probabilities by the side of the branches

**8.5- Summary and Review**

Probability – P(A ∪ B) and Mutually Exclusive Events

P(A ∪ B) = P(A) + P(B) – P(A ∩ B)

For mutually exclusive events, P(A ∩ B) = 0.

**8.6- Assessment 8**

Question 1 : What is the probability of a dice showing a 2 or a 5?

Question 2 : The probabilities of three teams A, B and C winning a badminton competition are 1/3, 1/5 and 1/9 respectively.

Calculate the probability that

a) either A or B will win

b) either A or B or C will win

c) none of these teams will win

d) neither A nor B will win

Question 3 : Three questions now from the higher level non-calculator paper. A fair spinner has five equal sections numbered 1, 2, 3, 4 and 5. A fair six-sided dice has five red faces and one green face. The spinner is spun. If the spinner shows an even number, the dice is thrown. Calculate the probability of getting an even number and the colour green?