##Statistics Seminar##\\ Department of Mathematical Sciences ^ **DATE:**|Thursday, November 15, 2018 | ^ **TIME:**|1:15pm -- 2:15pm | ^ **LOCATION:**|WH 100E | ^ **SPEAKER:**|Li, Kexuan, Binghamton University | ^ **TITLE:**|A proof of optimality of the Sequential Probability Ratio Test | \\ **Abstract** We present a proof that Wald's (1947) Sequential Probability Ratio Test for simple hypotheses delivers the smallest possible expected sample size under either hypothesis among all reasonable tests with fixed type I and type II error probabilities.