The hitchhiker's paradox is correct, taking a point and looking backward or forward will correctly give an average event 10 minutes away, but combining the events to give an average of 20 minutes is false.
I thought this sounded funny, and I did a little simulation to see if it was correct. Given his assumptions (poisson with lambda 10), you do not get that answer. I got right around 10, which is what I would expect.
Yes, it is true. I'm not sure what the first commenter is trying to say exactly. The second commenter's code was wrong, and correcting it gives the expected 20 minute average period.
Comments
This is the best explanation of the phenomenon. Simple and actually explains why it's 2x and not 3x or 4x.
Is it actually true though? Compare these two comments buried downthread:
https://news.ycombinator.com/item?id=16470358
https://news.ycombinator.com/item?id=16471544
Yes, it is true. I'm not sure what the first commenter is trying to say exactly. The second commenter's code was wrong, and correcting it gives the expected 20 minute average period.