“…Within this framework, Frisén (2003, 2007) showed that the Shewhart chart method, for which p ( x s )= L ( s , s ), maximizes the probability of detecting the outbreak at time T = s , and, asymptotically (as μ 1 increases), minimizes the time to detection, for a fixed false detection probability. In the Shiryaev–Roberts method (Shiryaev, 1963; Roberts, 1966), dependence on T through w ( s , t ) is eliminated by setting w ( s , t )=1, which may be justified asymptotically as corresponding to a vanishingly low probability of an outbreak.…”