A Study of the Correlation between the Articulation Competence Index (ACI) and the Percentage of Words Understood in the Continuous Speech of 4- and 5-year-olds of Varying Phonological Competence

Intelligibility refers to how recognizable a speaker\u27s words are to the listener. Severity, a broader but closely related concept, incorporates intelligibility, disability, and handicap. Many factors influence intelligibility, including speech sound production, voice, and prosody, as well as a number of linguistic and contextual factors. Clinicians and researchers in the field of speechlanguage pathology require accurate measures of intelligibility and severity to assess and describe communicative functioning and to measure change over time. Determining the most accurate and efficient measurement approaches has been the focus of recent attention in the field. This study was a preliminary investigation of the relationship between the Articulation Competence Index (ACI), a severity metric, and the percentage of words understood in continuous speech, the standard measure of intelligibility. Specifically, the study addressed the research question: Is there a significant correlation between the Articulation Competence Index (ACI) and percentage of words understood in samples of continuous speech of 4- and 5-year-olds with varying levels of phonological competence? Subjects were thirty 4- and 5-year-olds from the Portland metropolitan area. Four listeners calculated percentage-of-words scores for each child\u27s 100-word speech sample. These scores were compared to ACI scores calculated by the investigator for each of the samples. The data were analyzed using the Pearson productmoment correlation (Pearson£). A moderately strong correlation (£ = .71 to .81) was found between the ACI and percentage of words understood. Squaring the correlation coefficients resulted in values for £ 2 of .50 to .66, indicating that the ACI accounts for more than half the variability of continuous speech intelligibility