Navegando por Autor "Correa, Thais Rotsen"
Agora exibindo 1 - 3 de 3
Resultados por página
Opções de Ordenação
Item A critical look at prospective surveillance using a scan statistic.(2015) Correa, Thais Rotsen; Assunção, Renato Martins; Costa, Marcelo AzevedoThe scan statistic is a very popular surveillance technique for purely spatial, purely temporal, and spatialtemporal disease data. It was extended to the prospective surveillance case, and it has been applied quite extensively in this situation.When the usual signal rules, as those implemented in SaTScanTM( Boston, MA, USA) software, are used, we show that the scan statistic method is not appropriate for the prospective case. The reason is that it does not adjust properly for the sequential and repeated tests carried out during the surveillance. We demonstrate that the nominal significance level 𝛼 is notmeaningful and there is no relationship between 𝛼 and the recurrence interval or the average run length (ARL). In some cases, the ARL may be equal to ∞, which makes the method ineffective. This lack of control of the type-I error probability and of the ARL leads us to strongly oppose the use of the scan statistic with the usual signal rules in the prospective context.Item MAD-STEC : a method for multiple automatic detection of space-time emerging clusters.(2016) Veloso, Bráulio Miranda; Correa, Thais Rotsen; Prates, Marcos O.; Oliveira, Gabriel F.; Tavares, Andréa IabrudiCrime or disease surveillance commonly rely in space-time clustering methods to identify emerging patterns. The goal is to detect spatial-temporal clusters as soon as possible after its occurrence and to control the rate of false alarms. With this in mind, a spatio-temporal multiple cluster detection method was developed as an extension of a previous proposal based on a spatial version of the Shiryaev– Roberts statistic. Besides the capability of multiple cluster detection, the method have less input parameter than the previous proposal making its use more intuitive to practitioners. To evaluate the new methodology a simulation study is performed in several scenarios and enlighten many advantages of the proposed method. Finally, we present a case study to a crime data-set in Belo Horizonte, Brazil.Item Surveillance to detect emerging space time clusters.(2009) Assunção, Renato Martins; Correa, Thais RotsenThe interest is on monitoring incoming space time events to detect an emergent space time cluster as early as possible. Assume that point process events are continuously recorded in space and time. In a certain unknown moment, a small localized cluster of increased intensity starts to emerge. Its location is also unknown. The aim is to let an alarm to go off as soon as possible after its emergence, but avoiding that it goes off unnecessarily. The alarm system should also provide an estimate of the cluster location. In addition to that, the alarm system should take into account the purely spatial and the purely temporal heterogeneity, which are not specified by the user. A space time surveillance system with these characteristics using a martingale approach to derive the surveillance system properties is proposed. The average run length for the situation when there are clusters present in the data is appropriately defined and the method is illustrated in practice. The algorithm is implemented in a freely available stand-alone software and it is also a feature in a freely available GIS system.