Service oriented architectures (SoA) provide sharing of Web applications among enterprises by offering applications through Web services. However, SOAs correct operation depend on Web services availability. This paper proposes a hybrid model to Web service invocation combining the benefits of static and dynamic replication selection policy models. Through the proposed model the choice of the replica is based on statistical treatments performed on data collected from the replicates and on the detection of network conditions, unlike the solutions in the literature that are based on only one of these techniques. In future works the proposed model will be used to implement a prototype.