We consider optimal dynamic treatment regime determination in practice. Model building, checking, and comparison have had little or no attention so far in this literature. Motivated by an application on optimal dosage of anticoagulants, we propose a modeling and estimation strategy that incorporates the regret functions of Murphy (2003, Journal of the Royal Statistical Society, Series B 65, 331-366) into a regression model for observed responses. Estimation is quick and diagnostics are available, meaning a variety of candidate models can be compared. The method is illustrated using simulation and the anticoagulation application.

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Service is often provided in contexts where tasks or customers are impatient or perishable in that they have natural lifetimes of availability for useful service. Moreover, these lifetimes are usually unknown to the service provider. The question of how service might best be allocated to the currently waiting tasks or customers in such a context has been neglected and we propose three simple models. For each model, an index heuristic is developed and is assessed numerically. In all cases studied the heuristic comes close to optimality.

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The incidence of ankle injury in youth soccer is higher in competition, and increases with age in competition. 17.5% of ankle injuries missed more than 6 weeks' training, but the authors found a subgroup of players with delay in returning to sport in whom there was no further investigation to establish the diagnosis. This group may harbour occult injury to the chondral surfaces, and earlier investigation could minimise secondary joint damage in this 'at risk' age group.