Probabilities are placed on a scale. Between which two numbers does every probability lie, counting the ends of the scale themselves?

Explication

The scale runs from an event that never happens up to one that always happens, and those two extremes are written as 0 and 1, so nothing falls outside that stretch. Answering 0 and 100 borrows the percentage scale, which measures the same idea in different units, but a probability written as an ordinary number stops at 1.