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.