14. The system of claim 12 , wherein the predetermined feedback score is determined before determining that the received voice input is classified as feedback that indicates satisfaction or dissatisfaction with the provided answer to the question.
12. A system comprising: a non-transitory computer readable medium having instructions stored thereon; and data processing apparatus programmed to execute the instructions to perform operations comprising: providing, by a dialog engine, an answer to a question; after providing the answer to the question, receiving, by the dialog engine, a voice input; determining, by the dialog engine, that the received voice input is classified as feedback that indicates satisfaction or dissatisfaction with the provided answer to the question; identifying, by the dialog engine, a predetermined feedback score that reflects an extent to which, in response to other questions, other users express satisfaction or dissatisfaction when speaking a particular term that is included in the received voice input; adjusting, based at least on the predetermined feedback score that is associated with a transcription of the received voice input, a confidence score that, based on prior selections of the provided answer to the question by other users, indicates an estimation of relevance of the provided answer to the question; and in response to a subsequent receipt of the question, selecting, by the answer generation engine, the answer or a different answer based at least on the adjusted confidence score.