1. theoretical probability p = number of successful outcomes
total possible outcomes
Example
Find the probability of scoring a 3 on an unbiased 6 sided die 1 6
number of successful outcomes (one 6 on the die)
total possible outcomes (6 possible outcomes)
experimental probability or relative frequency
p = number of successful outcomes
total number of trials
Example
Complete a relative frequency table from these results:
The recorded results of a 5 sided spinner being spun R is Red, Y is Yellow, B is Blue
R, B, R, Y, Y, R, B, Y, R, R, Y, B, B, R, Y, R, Y, R, B, R
Colour
Red
Yellow
Blue
Frequency 9 6 5
Relative Frequency 20
The probability of the spinner
landing on a yellow is: 5 20

2. Probability Tree Diagrams
A tree diagram for whether it is raining or not
rain
The outcome is written at the end of the branch
not rain