Your sampling is biased, and so is your estimator. You're way off.
A. Hipster wrote:
I know four people who ran that much or more. Here is the math to extrapolate how many people ran that much or more in the whole world:
I know almost 500 people (number of facebook friends I have). Out of those, 4 people ran 102 or more mile last week. That comes out to .008 (or .8%). The population of the world is 6.94 billion. To figure out how many ran 102 or more miles last week, you simply multiply 6.94 billion by .008. It comes out to 55.5 million.
I thought I saw a lot of runners out this week.