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Relationships Among Consistency/Variability and Other Phonological Measures Over Time

Tyler, Ann A. PhD; Lewis, Kerry E. PhD


This article explores selected phonological measures, their relationships to one another, and how groups differentiated by such measures change over time during intervention. Relationships among global quantitative measures of severity (percent consonants correct), measures of variability/consistency, and measures of whole-word complexity and syllable shape from 40 children with speech sound disorders were examined. All relationships were strong prior to intervention and remained stable during the course of intervention. Groups of 10 were differentiated with the measure of variability so that a variable group had many different error substitutions and the consistent group had few different error substitutions across the system. For these 2 groups, comparison of change at 3 points during the course of a 24-week intervention showed trends that were markedly similar in their linearity. There was steady improvement in percent consonants correct scores over time and a graduated decrease in the variability of errors on target sounds. The lack of a discernable difference between the consistent and variable groups in their response to the same intervention is seen as evidence to suggest that such groups may not need different types of intervention.

School of Medicine, Department of Speech Pathology and Audiology, University of Nevada, Reno.

Corresponding author: Ann A. Tyler, PhD, School of Medicine, Department of Speech Pathology and Audiology, Nell J. Redfield Bldg/152, Reno, NV 89557 (e-mail:

© 2005 Lippincott Williams & Wilkins