10. A computer readable medium comprising a set of instructions which, when executed by a computer, cause the computer to combine probability of click models in an online advertising system, said instructions for: receiving, at a computer, at least one feature set slice; training, in a computer, a plurality of slice predictive models, the slice predictive models corresponding to at least a portion of the features in the at least one feature set slice; assigning weights, in a computer, to at least two of the plurality of slice predictive models by overlaying a weighted distribution model over the plurality of slice predictive models; and calculating, in a computer, a combined predictive model based on the at least two of the plurality of slice predictive models and their assigned weights.
10. A computer readable medium comprising a set of instructions which, when executed by a computer, cause the computer to combine probability of click models in an online advertising system, said instructions for: receiving, at a computer, at least one feature set slice; training, in a computer, a plurality of slice predictive models, the slice predictive models corresponding to at least a portion of the features in the at least one feature set slice; assigning weights, in a computer, to at least two of the plurality of slice predictive models by overlaying a weighted distribution model over the plurality of slice predictive models; and calculating, in a computer, a combined predictive model based on the at least two of the plurality of slice predictive models and their assigned weights. 13. The computer readable medium of claim 10 , wherein the combined predictive model p(c|x) is calculated using the formula: p ⁡ ( c | x ) = ∑ i = 1 K ⁢ α i ⁢ p i ⁡ ( c | x ) .