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Discussion on: Memorylessness at the Bus Stop: Using R on transit data to test a hypothesis

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Walker Harrison

I agree with everything you've said -- the game you describe is an instance of the geometric distribution, which is memoryless and the discrete case analogue to the exponential distribution. And yes, committing yourself to waiting for 20 minutes as opposed to 5 or 10 will by definition expose you to a higher probability of the bus coming.

The point of my article, and the thing about memoryless that for me at least is fascinating and spooky, is that your odds never improve even after waiting. It's a counterintuitive idea -- you'd think that since a bus must be on the way, your chances should be improving with every passing minute, when in fact they are not. Personally, I find that pretty cool!