1. Assessing Speech Intelligibility and Severity
What are some standard procedures?

2. Are measures of intelligibility and severity the same?
Although judgements about intelligibility and severity may be correlated, they represent two different indices about an individual’s speech
For example, a child may have a severe resonance disorder, but his/her speech is still intelligible

3. Intelligibility Scales
Typically a panel of 2-5 listeners (expert ~ novice; familiar ~ unfamiliar) rate a taped (audio or video) segment of child’s speech
Rank intelligibility of child’s speech compared to age peers
Scales typically use 3-point or point judgment scales (See Bleile)
scores are averaged to derive a composite intelligibility rating score

4. Intelligibility Scales
Kent, Miolo, & Bloedel (1994) compared 19 intelligibility measures according to 5 categories that differed with regard to the emphasis of the analysis (phonetic ~ phonemic; word level ~ conversation)

5. Intelligibility Scales
Listed 8 factors that influence clinical evaluation of intelligibility:
loss of phonological contrasts
loss of contrasts in specific environments
extent of homonymy
amt of difference between target~realization
frequency of occurrence in English
consistency
familiarity of listener with speaker
context in which communication occurs

6. Intelligibility
Weston & Shriberg (1992) concluded that articulation variables alone cannot account for all the breakdowns that result in communication
other general contextual and linguistic variables are related to speech intelligibility

7. Severity
Similar to intelligibility rating scales, a panel of familiar or unfamiliar listeners judge a segment of a child’s recorded (audio or video-taped) speech (single word or connected speech)

8. Severity Perceptual scales (see Bleile) or quantitative measures
4 Point Clinical Judgement Scale of Severity
No disorder-Mild-Moderate-Severe
average score of 3.5 often required to provide clinical services

9. Severity Quantitative Measures PCC (and 8 variations) Hodson’s PDS
Edwards’ PDI

10. Comparison of PCC and PDS Severity Ratings
Mild >90%
Mild-Mod 65-85%
Mod-Sev 50-65%
Severe <50%
PDS
Mild pts
Moderate 20-39
Severe 40-59
Profound 60+

11. Shriberg, Austin, Lewis, McSweeny, & Wilson (1997)
9 speech metrics
PCC (based on conv speech)
PCC-A (common clinical distortions scored correct)
PCC-R ([un]common distortion scored correct)
ACI (differentially weighs distortion ~ sub/omis)
PCI (percentage of sounds mastered-early talkers)
PVC (similar to PCC, but for vowels/diphthongs)
PVC-R (similar to PCC-R, but for vowels/diphthongs)
PPC (percentage to consonants/vowels correct)
PPC-R (scores distortions correct)

12. Which metric is most appropriate?
Depends on specific needs of the assessment
Interest limited to consonants
PCC, PCC-A, PCC-R, ACI
Young/severely delayed children
PCI
Interest in vowels/diphthongs
PVC, PVC-R
Interest in articulation competence on all speech sounds
PPC, PPC-R

13. Rafaat, Rvachew, & Russell (1995)
Purpose of study was to determine the percentage of agreement between SLPs in rating PI severity
Adequate reliability for older children (4;6+), but unreliable for children under 3;6
Unable to reliably distinguish TD from mild delay

14. Why were SLPs less reliable on severity ratings of younger children?

15. What factors account for differences in reliability ratings?