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Research in normal and disordered phonology requires measures of speech production that are biolinguistically appropriate and psychometrically robust. Their conceptual and numeric properties must be well characterized, particularly because speech measures are increasingly appearing in large-scale epidemiologic, genetic, and other descriptive-explanatory database studies. This work provides a rationale for extensions to an articulation competence metric titled the Percentage of Consonants Correct (PCC; Shriberg & Kwiatkowski, 1982; Shriberg, Kwiatkowski, Best, Hengst, & Terselic-Weber, 1986), which is computed from a 5- to 1 0-minute conversational speech sample. Reliability and standard error of measurement estimates are provided for 9 of a set of 10 speech metrics, including the PCC. Discussion includes rationale for selecting one or more of the 10 metrics for specific clinical and research needs.
KEY WORDS: phonology, articulation, speech disorders, assessment, measurement
Alucid tutorial review by Kent, Miolo, and Bloedel (1994) provides comparative analysis of 19 procedures that researchers and clinicians have used to assess intelligibility of speech in children. Although the focus is on intelligibility assessment, rather than on measures that index severity of speech involvement, the procedures included in this tutorial and the discussion of relevant psychometric issues provide good coverage of the state of the art in the measurement of speech disorder in children. Kent and colleagues divide their evaluative analysis of assessment procedure into five primary categories, including those that emphasize phonetic contrast analyses, phonological analyses, word identification, scaling methods, and phonetic accuracy in continuous speech. In the present context, the most salient observation these authors underscore is "the relatively little work that has been done to evaluate the reliability and validity of the procedures developed to date" (p. 90).
The present work addresses reliability and validity issues for an approach to speech assessment that Kent and colleagues subsumed under the category of phonetic accuracy in continuous speech. This work continues the directions suggested in an earlier article providing rationale and validity data for several speech and prosody-voice measures for genetics research and other descriptive studies in developmental phonological disorders (Shriberg, 1993). Each metric is derived from a conversational speech sample, including a procedure to obtain an index of intelligibility in natural conversational speech. The present work adds information to the earlier report in the following areas: (a) descriptions of...