# Perplexity, log probabilities and smoothing

Subject: Natural Language Processing

Exam: TEE

Reader: https://deep-learning-study-room.vercel.app/nlp/#tee/read/m2-evaluation-smoothing

Canonical: https://deep-learning-study-room.vercel.app/read/nlp/tee/read-chapter/m2-evaluation-smoothing/

Unit 3, pages 121–156

1. [Perplexity: meaning, formula and four complete examples](https://deep-learning-study-room.vercel.app/read/nlp/tee/read/m2-evaluation-smoothing--evaluation-perplexity/)
2. [Log probabilities: replace long products with sums](https://deep-learning-study-room.vercel.app/read/nlp/tee/read/m2-evaluation-smoothing--log-probabilities/)
3. [Laplace smoothing: why both numerator and denominator change](https://deep-learning-study-room.vercel.app/read/nlp/tee/read/m2-evaluation-smoothing--laplace-basics/)
4. [A complete unseen-bigram question from corpus to final answer](https://deep-learning-study-room.vercel.app/read/nlp/tee/read/m2-evaluation-smoothing--smoothed-sentence/)
5. [Adjusted counts and relative discounting](https://deep-learning-study-room.vercel.app/read/nlp/tee/read/m2-evaluation-smoothing--adjusted-count-discount/)
6. [Character-model perplexity: keep exact probabilities](https://deep-learning-study-room.vercel.app/read/nlp/tee/read/m2-evaluation-smoothing--class-perplexity-characters/)