In this article, we introduce the application of rigorous analysis procedures to goal models to provide several beneรts beyond the initial act of modeling. Such analysis can allow modelers to assess the satisfaction of goals, facilitate evaluation of high-level design alternatives, help analysts dec
Improved language modelling through better language model evaluation measures
โ Scribed by Philip Clarkson; Tony Robinson
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 172 KB
- Volume
- 15
- Category
- Article
- ISSN
- 0885-2308
No coin nor oath required. For personal study only.
โฆ Synopsis
This paper explores the interaction between a language model's perplexity and its effect on the word error rate of a speech recognition system. Much recent research has indicated that these two measures are not as well correlated as was once thought, and many examples exist of models which have a much lower perplexity than the equivalent N -gram model, yet lead to no improvement in recognition accuracy. This paper investigates the reasons for this apparent discrepancy. Perplexity's calculation is based solely on the probabilities of words contained within the test text; it disregards the probabilities of alternative words which will be competing with the correct word within the decoder. It is shown that by considering the probabilities of the alternative words it is possible to derive measures of language model quality which are better correlated with word error rate than perplexity is. Furthermore, optimizing language model parameters with respect to these new measures leads to a significant reduction in the word error rate.
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Language models are usually evaluated on test texts using the perplexity derived from the model likelihood function computed on these texts (test set perplexity). In order to use this measure in the framework of a comparative evaluation campaign, we have developed an alternative scheme for estimatin
where B and C are nonstochastic matrices of the appropriate order in each case. When additionally B is symmetric, However, in the article, only the first result was utilized, with no serious consequences, as the matrix B is symmetric. The other results in (4) are correct.