Norms Across all three assessments

Total Group

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MacArthur-Bates Communicative Development Inventories (CDI), Second Edition (Fenson, Marchman, Thal, Dale, Reznick & Bates, 2006).

There are three different versions of the CDI, one for infants from 6 to 18 months, one for toddlers from 18 to 30 months, and one for children from 30 to 37 months.
The infant form assesses receptive and expressive vocabulary as well as the use of communicative and symbolic gestures.
The toddler form assesses productive vocabulary, and the early phases of grammar. The most advanced form evaluates vocabulary production and grammar.
Each of these forms has been modified in our laboratory so as to assess spoken and signed vocabulary separately.
Extensive testing reveals good internal consistency (alphas from .67 – .96) and test-retest reliability (.86 – 95) (See Dale, Bates, Resnick, & Morriset, 1989).
Children should be given the appropriate version of the MacArthur depending on the family’s and interventionist’s assessment of the child’s language ability.
The inventories are parent-completed, norm-referenced instruments based on the performance of 1,789 normally developing infants and toddlers 8 to 30 months of age.