6. The method of claim 5 , wherein selecting the sample utterance-to-text-string mappings from the corpus of utterance-to-text-string mappings based on the compressed word frequencies c i further comprises: determining a second word selection probability for a second word based on a second compressed word frequency of the second word divided by a second word frequency of the second word, wherein the particular text string also contains the second word; and selecting the particular utterance based on the first word selection probability and second word selection probability.
7. The method of claim 6 , wherein selecting the particular utterance based on the first word selection probability and second word selection probability comprises: calculating an arithmetic mean of the first word selection probability and the second word selection probability; and selecting the particular utterance with a probability of the arithmetic mean.