The Intelligibility in Context Scale: Validity and Reliability of a Subjective Rating Measure PurposeTo 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).MethodSpeech ... Research Note
Research Note  |   April 01, 2012
The Intelligibility in Context Scale: Validity and Reliability of a Subjective Rating Measure
 
Author Affiliations & Notes
  • Sharynne McLeod
    Charles Sturt University, Bathurst, New South Wales, Australia
  • Linda J. Harrison
    Charles Sturt University, Bathurst, New South Wales, Australia
  • Jane McCormack
    Charles Sturt University, Bathurst, New South Wales, Australia
  • Correspondence to Sharynne McLeod: smcleod@csu.edu.au
  • Editor: Anne Smith
    Editor: Anne Smith×
  • Associate Editor: Fiona Gibbon
    Associate Editor: Fiona Gibbon×
Article Information
Research Issues, Methods & Evidence-Based Practice / Speech
Research Note   |   April 01, 2012
The Intelligibility in Context Scale: Validity and Reliability of a Subjective Rating Measure
Journal of Speech, Language, and Hearing Research, April 2012, Vol. 55, 648-656. doi:10.1044/1092-4388(2011/10-0130)
History: Received May 14, 2010 , Revised December 11, 2010 , Accepted August 25, 2011
 
Journal of Speech, Language, and Hearing Research, April 2012, Vol. 55, 648-656. doi:10.1044/1092-4388(2011/10-0130)
History: Received May 14, 2010; Revised December 11, 2010; Accepted August 25, 2011
Web of Science® Times Cited: 32

PurposeTo 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).

MethodSpeech 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.

ResultsParents' 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).

ConclusionsThe 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.

Acknowledgments
This research was supported by the following sources: Australian Research Council Discovery Grant DP0773978; Australian Research Council Future Fellowship FT0990588; and the Charles Sturt University Research Institute for Professional Practice, Learning and Education. The authors acknowledge the insights, assistance, and support of Lindy McAllister, Christine Porter, Bethany Toohill, Emma Heinrich, and Hannah Wilkin.
Order a Subscription
Pay Per View
Entire Journal of Speech, Language, and Hearing Research content & archive
24-hour access
This Article
24-hour access