From an hour to half an hour
On a stretch of road, the probability of observing at least one accident during any given hour is 3/4. Accidents happen independently of each other at a constant average rate.
What is the probability of observing at least one accident during a half-hour period?
The naive answer, 3/8, is wrong.
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Work with the probability of no accident. An hour is two independent half-hours.
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