Comparing the Diversity of Lexical Categories: the Type-Type Ratio and Related Measures

Abstract

The aim of this chapter is to provide an empirical demonstration of the sensitivity of type-type ratios to sample size and to outline and demonstrate a solution derived from the mathematical modelling procedures described in earlier chapters. However, because researchers working in language development and education are probably less aware of the problems related to sample size for type-type ratios than they are for type-token ratios, and because of the significance for theory and practice of recent research that has used such measures, we will begin with an extensive review of the issues. This will encompass analyses of rare words or lexical sophistication, studies of vocabulary composition and early lexical style, and of the ‘noun bias’ issue.