Probabilities can be shown on a scale between 0 (impossible) and 1 (certain).
For example, imagine a shopping bag contains three bananas and nothing else:
The probability of reaching into the bag and pulling out a banana is 1 (certain), as there is nothing else in the bag.
The probability of reaching into the bag and pulling out an apple is 0 (impossible), as there are no apples in the bag.
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