What is probability?
Answer
Probability is a measure of how likely an event is to happen, calculated as the number of favourable outcomes divided by the total number of equally likely outcomes.
The working
Formula
For equally likely outcomes, P(E) = (number of favourable outcomes) / (total number of outcomes).
Range
The probability of any event always lies between 0 and 1, where 0 means impossible and 1 means certain.
Complement
The probability that an event does not happen is P(not E) = 1 − P(E), since all probabilities of an experiment add up to 1.
Example
For a fair die, the probability of getting a 4 is 1/6, because there is one favourable outcome out of six equally likely outcomes.
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