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.
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. 16. The system of claim 12 , wherein determining that the received voice input is classified as feedback that indicates satisfaction or dissatisfaction with the provided answer comprises: determining an amount of time that elapses between providing the answer to the question and receiving the voice input; and determining that the amount of time that elapses between providing the answer to the question and receiving the voice input is less than a predetermined amount of time.