Home Practice
For learners and parents For teachers and schools
Full catalogue
Learners Leaderboard Classes/Grades Leaderboard Schools Leaderboard
Pricing Support
Help centre Contact us
Log in

We think you are located in United States. Is this correct?

Chapter summary

Test yourself now

High marks in science are the key to your success and future plans. Test yourself and learn more on Siyavula Practice.

Sign up and test yourself

26.5 Chapter summary

  • Probability is a way of describing how likely an event is to occur.
  • An experiment is a test that we do to find out if something is true or to learn something. It is an uncertain process.
  • An outcome is a single result of an experiment.
  • The sample space (\(S\)) is the set of all possible outcomes of that experiment.
  • The size of the sample space (the total number of possible outcomes) is written as \(n(S)\).
  • An event (\(E\)) is a specific set of outcomes of an experiment that you are interested in.
  • The number of outcomes in the event is written as \(n(E)\).
  • An event that is described as “impossible” has a probability of \(0\).
  • An event that is described as “certain” has a probability of \(1\).
  • Probabilities can be expressed as decimal fractions between \(0\) and \(1\); or percentages between \(0 \%\) and \(100 \%\); or fractions between \(0\) and \(1\).
  • The probability of an event is the number of outcomes in the event set divided by the number of possible outcomes in the sample space: \(P(E) = \frac{n(E)}{n(S)}\).
  • Frequency is the number of times an event occurs.
  • Relative frequency is the observed number of outcomes for a certain number of trials.
  • Relative frequency \((f)\) is calculated by dividing the number of positive outcomes \((p)\) by the total number of trials \((t)\): \(f = \frac{p}{t}\)
  • As the number of trials increases, the relative frequency gets closer to the theoretical probability.