Why do speech prostheses report words per minute and error rates instead of bits per minute? · Lobeworks/17

The bit rate assumes a fixed set of equally likely options, and speech has neither: a vocabulary of a hundred thousand words, used with very unequal frequencies, and a language model that makes some sentences far more expected than others.

Why do speech prostheses report words per minute and error rates instead of bits per minute?

The bit rate assumes a fixed set of equally likely options, and speech has neither: a vocabulary of a hundred thousand words, used with very unequal frequencies, and a language model that makes some sentences far more expected than others. Words per minute says how fast a person talks, the word error rate says how much of it was wrong, and the two together describe the trade a user lives with. A rate quoted without its error rate describes half of it.