Query expansion using mutual information between words in question and its answer

Question Answering (QA) is a task of answering natural language questions with an adequate sentence. This paper proposes to improve the query expansion in the relevant document retrieval module. We proposed modification of measure of mutual information for the query expansion; we calculate it between two words of a question and a word in its answer in the Q & A site corpus not to choose the words that are not suitable. The experiments with Japanese Q & A site corpus revealed that the proposed method significantly improved the accuracies and MRRs (Mean Reciprocal Rank).