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# Test yourself now

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

## 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.