Predicting the out-of-vocabulary rate and the required vocabulary size for speech processing applications

The paper describes an approach for predicting both the vocabulary size and the resulting out-of-vocabulary rate (OOV rate) for a hypothetical extension of an existing text corpus. By splitting the original corpus into two different sub corpora, vocabulary and OOV rate can be determined for that special constellation. Average values are calculated for all combinations of sub corpora and can be approximated by analytic function terms. These functions enable the easy prediction of vocabulary size and OOV rate. The prediction accuracy results in a relative error below 4.6%.