In Mathematics, the correct name for chance is ‘probability’. Probability is the branch of Mathematics that allows us to calculate how likely (or unlikely) it is that an event will happen.


Probability is the chance (or likelihood) of something happening.


An event or outcome is a possible result in an experiment. The probability of an event is how likely it is that the event will occur. Simple events are where one experiment happens at a time and it will have a single outcome.


Examples of events could be: ● ●


●


getting ‘tails’ when tossing a coin rolling a ‘7’ with two dice


picking a number that is odd or even. The probability of simple events is denoted by P(E) where E is the event. It is said as ‘probability of an event’.


The probability of an event ocurring (or not occurring) will always lie between 0 and 1. For example, tossing a coin is an example of a simple probabilty experiment, the events (outcomes) of this experiment are heads or tails:


P(heads) = 1


__ 2 and P(tails) = 1


__ 2


Another example could be using a spinner. The outcome of this experiment is the spinner landing on a particular colour. If Chloe spins a spinner and it lands on green: ●


the experiment is spinning the spinner ● the event (or outcome) is the colour the spinner lands on.


These can be said to be the events connected with the experiment. So when the spinner lands on green, an event can be said to have occurred.


The mathematical language of probability


To understand probability, we must understand the language used to desribe the chances of something happening. For example:


What is the likelihood of rain today? What’s the probability my bus will arrive on time?


What are the chances our school will win the league cup this year? ● ●


● Language used to describe probability of an event


impossible 0


0%


very unlikely to happen


not likely to happen


_ 2


1 0.5


equal chance of happening as not happening


very likely to happen


likely to happen


certain 100% 1


If something is certain to happen, it has a probability of 1 (or 100%).


If something is certain not to happen (impossible) it has a probability of 0 (or 0%).


All other events have a probability between 0 and 1 (0% and 100%).


You cannot have a negative value for probability.


The probability of an event can be expressed as a fraction, decimal or percentage.


Section A Introducing concepts and building skills


95


6 Probability 1


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