1. A computer-implemented method comprising: obtaining information regarding selections of search results provided in response to a plurality of search queries, the obtained information for one or more of the selected search results comprising one or more presentation bias features of a presentation of the search result and one or more relevancy features of the search result, wherein at least one of the presentation bias features is a rank of the search result in the search results; training a model using the obtained information, wherein the model is trained to predict a click through rate based on input comprising the one or more presentation bias features and the one or more relevancy features; and providing the model for use with a search engine, wherein the search engine is configured to provide presentation bias and relevancy features of given search results as input to the model and to use predictive outputs of the model to reduce presentation bias in a presentation of the given search results by determining a quality score for each of the given search results and factoring out independent effects of presentation bias from the quality scores using the predictive outputs of the model, wherein the predictive outputs used to reduce the presentation bias in the presentation of the given search results include a predicted click through rate predicted based on the presentation bias and relevancy features of the given search results and the model.
8. The method of claim 1 wherein the search engine is further configured to use comparisons of the predictive outputs of the model with an implicit user feedback model to adjust respective ranking scores of the given search results.