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Comparing productive vocabulary measures from the CDI and a systematic diary study

Published online by Cambridge University Press:  01 February 1999

BYRON F. ROBINSON
Affiliation:
University of Louisville
CAROLYN B. MERVIS
Affiliation:
University of Louisville

Abstract

Expressive vocabulary data gathered during a systematic diary study of one male child's early language development are compared to data that would have resulted from longitudinal administration of the MacArthur Communicative Development Inventories spoken vocabulary checklist (CDI). Comparisons are made for (1) the number of words at monthly intervals (9;10.15 to 2;0.15), (2) proportion of words by lexical class (i.e. noun, predicate, closed class, ‘other’), (3) growth curves. The CDI underestimates the number of words in the diary study, with the underestimation increasing as vocabulary size increases. The proportion of diary study words appearing on the CDI differed as a function of lexical class. Finally, despite the differences in vocabulary size, logistic curves proved to be the best fitting model to characterize vocabulary development as measured by both the diary study and the CDI. Implications for the longitudinal use of the CDI are discussed.

Type
NOTE
Copyright
© 1999 Cambridge University Press

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Footnotes

We thank John Pani and Cindy Mervis for help with data collection. Cindy Mervis and Kathy Johnson performed much of the data reduction and organization of the original diary. Data collection was supported by National Science Foundation Grant BNS 84-19036. Analysis and preparation of this article were partially supported by National Institutes of Child Health and Human Development Grant HD 29957.