of this decomposition result, stopping times do not have to be almost surely finite, and can equal ∞. Stopping rules in clinical trials Clinical trials in medicine often perform interim analysis, in order to determine whether the trial has already met its endpoints. However, interim analysis create the risk of false-positive results, and therefore stopping boundaries are used to determine the number and timing of interim analysis (also known as alpha-spending, to denote the rate of false positives). At each of R interim tests, the trial is stopped if the likelihood is below a threshold p, which depends on the method used. See Sequential analysis. See also Optimal stopping Odds algorithm Secretary problem Hitting time Stopped process Disorder problem Début theorem Sequential analysis References Further reading Thomas S. Ferguson, “Who solved the secretary problem?”, Stat. Sci. vol. 4, 282–296, (1989). An introduction to stopping times. F. Thomas Bruss, “Sum the odds to one and stop”, Annals of Probability, Vol. 4, 1384–1391,(2000) Stochastic processes Optimal decisions