15. A non-transitory computer-readable storage medium storing instructions which, when executed by a computing device, cause the computing device to perform steps comprising: identifying, in a database of utterances, first transcribed utterances and first un-transcribed utterances; identifying transcription candidate utterances from the first un-transcribed utterances; predicting likely recognition error utterances from the transcription candidate utterances; forwarding the likely recognition error utterances to a transcriber, to yield additional transcribed utterances; adding the additional transcribed utterances to the database of utterances, to yield an updated database of second transcribed utterances and second un-transcribed utterances; and if word accuracy has converged, modifying an automatic speech recognition system by providing both the second transcribed utterances and the second un-transcribed utterances to the automatic speech recognition system.
19. The non-transitory computer-readable storage medium of claim 15 , wherein a word is considered to be correctly recognized if the word has a confidence score higher than a threshold value.