The modern service economy is substantively different from the agricultural and manufacturing
economies that preceded it. In particular, the cost of experimenting is dominated by
opportunity cost rather than the cost of obtaining experimental units. The different economics
require a new class of experiments, in which stochastic models play an important role. This
article briefly summarizes mulit-armed bandit experiments, where the experimental design is
modified as the experiment progresses to make the experiment as inexpensive as possible.