1. A computer-implemented method comprising: providing a probability tree of nodes in which each node is associated with a tries value and a success value, and at least one node is associated with a computed probability value representative of a predicted response rate for an advertisement creative; and computing a first probability value for a first node of the probability tree based on its associated tries value and success value, and a computed probability value associated with a parent node to the first node, wherein the first probability value is computed based on an algorithm that generates a probability value approximately equal to that of the parent node to the first node when the success value associated with the first node approaches zero.