Not so rare for rarities to occur in waves: Professor

Scary numbers have dominated Toronto headlines this month: Seven dead in seven days.
Published : January 29, 2010

Scary numbers have dominated Toronto headlines this month: Seven dead in seven days.

Fourteen pedestrians killed across the GTA. The deadliest January for city pedestrians in a decade.

No wonder people are walking scared.

There is a tendency to grip these disturbing numbers and wring them for meaning. But for statisticians, maybe there is no meaning behind the numbers, just probability.

“Chances of a big clump are more than you would think,” said Jeffrey Rosenthal, a professor of statistics at the University of Toronto. “Yes, (the numbers) are rare and January was certainly much worse than usual, but it wasn’t something that is completely unexpected.”

Plane crashes, lightning strikes — for probability theorists, it’s no surprise that such rare happenings often occur in waves.

Rosenthal, who authored Struck by Lightning: The Curious World of Probabilities, explains that random events are all subject to a statistical phenomenon called Poisson bursts, named for the 19th-century mathematician Siméon Denis Poisson.

 
 
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