The Intelligibility in Context Scale: Validity and Reliability of a Subjective Rating Measure

TLDR

To describe a new measure of functional intelligibility, the Intelligibility in Context Scale (ICS), and evaluate its validity, reliability, and sensitivity using three clinical measures of speech sound disorder severity. Parents completed a 7‑item scale rating intelligibility across seven communication partners on a 5‑point scale, and factor analysis confirmed internal consistency, allowing the items to be averaged into an overall score. The scale showed high internal reliability (α = .93), strong construct validity, and significant correlations with PPC, PCC, and PVC (r = .54, .54, .36), supporting its validity and reliability as an estimate of preschool children’s intelligibility.

Abstract

To describe a new measure of functional intelligibility, the Intelligibility in Context Scale (ICS), and evaluate its validity, reliability, and sensitivity using 3 clinical measures of severity of speech sound disorder: (a) percentage of phonemes correct (PPC), (b) percentage of consonants correct (PCC), and (c) percentage of vowels correct (PVC).Speech skills of 120 preschool children (109 with parent-/teacher-identified concern about how they talked and made speech sounds and 11 with no identified concern) were assessed with the Diagnostic Evaluation of Articulation and Phonology (Dodd, Hua, Crosbie, Holm, & Ozanne, 2002). Parents completed the 7-item ICS, which rates the degree to which children's speech is understood by different communication partners (parents, immediate family, extended family, friends, acquaintances, teachers, and strangers) on a 5-point scale.Parents' ratings showed that most children were always (5) or usually (4) understood by parents, immediate family, and teachers, but only sometimes (3) by strangers. Factor analysis confirmed the internal consistency of the ICS items; therefore, ratings were averaged to form an overall intelligibility score. The ICS had high internal reliability (α = .93), sensitivity, and construct validity. Criterion validity was established through significant correlations between the ICS and PPC (r = .54), PCC (r = .54), and PVC (r = .36).The ICS is a promising new measure of functional intelligibility. These data provide initial support for the ICS as an easily administered, valid, and reliable estimate of preschool children's intelligibility when speaking with people of varying levels of familiarity and authority.