Which measurement assesses vocabulary diversity by calculating the ratio of unique words to the total number of words?

The measurement that assesses vocabulary diversity by calculating the ratio of unique words to the total number of words is known as the Type-Token Ratio (TTR). This metric is widely used in linguistic studies to evaluate the richness of a person's vocabulary in a given text. By taking the number of distinct words (types) and dividing it by the total number of words (tokens), TTR provides insight into how varied or diverse the vocabulary is within that text. A higher TTR indicates a more diverse vocabulary, suggesting that the text employs a wider range of words, while a lower TTR may indicate repetitiveness or a limited vocabulary.

The other options reflect various approaches to measuring aspects of vocabulary or language use, but they do not specifically measure the ratio of unique words to total words in the way TTR does. For example, a Lexical Diversity Index might incorporate additional factors or different methodologies to derive its score, and the Vocabulary Richness Score could include qualitative assessments beyond mere counts of unique and total words. Word Frequency Ratio usually refers to the frequency at which words appear rather than focusing on the unique versus total word count.