the.com/random walk
a drunk taking steps with no memory of where they just were
means a mathematical process where each next step is random and independent of the direction of the last one
from coined around 1905 in a note by karl pearson in nature, asking the odds of finding a wandering mosquito, and answered days later by lord rayleigh using old work on sound wave diffusion
return guaranteein 1d and 2d, walker returns home with probability 1
3d escapein 3d, chance of ever returning is only 34 percent
drunk analogykarl pearson literally called it the drunkard's walk
market theoryused to argue stock prices are basically unpredictable
for instance
brownian motion — pollen grains jittering in water, observed by robert brown, 1827
stock market prices — burton malkiel's 1973 book argued wall street moves like this
google pagerank — models a random surfer clicking links to rank web pages, 1998
gambler's ruin — classic problem of a bettor's fortune wandering to zero