1. A computerized yield management system, comprising: pre-processing computing device means executed by a data pre-processor in a computer processing unit for pre-processing an input data set comprising one or more prediction variables and one or more response variables containing data about a particular semiconductor process, the pre-processing computing device means further comprising means for removing one or more prediction variables from the input data set having more than a predetermined number of missing values, means for removing one or more prediction variables from the input data set having more than a predetermined number of classes, and means for removing data having more than a predetermined number of missing values to generate pre-processed data; model generating computer device means executed by a model builder in the computer processing unit, the model builder being in communication with the data pre-processor, for generating a model based on the pre-processed data, the model being a decision tree; computing device means executed by the model builder for modifying the model based on user input; and computing device means executed by a statistical tool library in the computer processing unit, the statistical tool library being in communication with the model builder, for analyzing the model using a statistical tool to generate one or more key yield factors based on the input data set.