Sensitivity of Various PCC-Type Measures and Phoneme Acquisition Measures
Ann Bosma Smit
Kansas State University
asmit@ksu.edu
Klaire Mann Brumbaugh
Bluebonnet Trails Early
Childhood Intervention
(Austin, TX)
Barbara Weltsch
Melanie Hilgers
Kansas State University Kansas State University
Presented at the Annual Convention of the Kansas Speech-Language-Hearing Association, September 25,
2015.
Disclosure Statement: Dr. Smit, Ms. Brumbaugh, Ms. Weltsch, and Ms. Hilgers have no relevant financial
or nonfinancial relationships to disclose.
Introduction
If a client is a preschooler with phonological disorder (PD), how much change can the SLP expect in such
a child’s phonology in a given period of intervention? This is an important question, especially in the age
of evidence-based practice. However, the answer is not readily apparent, and one possible reason is
that there may be problems with the measures. Smit's (2014) review of PCC in conversation (PCCconv) and
PCC in a word list (PCClist) found that studies that reported relatively high rates of improvement in PCC,
for example, estimated gain in PCCconv of 1.0% per week of intervention or 1.5% per week in PCClist, did
not maintain adequate measures against bias in transcription. In contrast, the studies that reported
stringent precautions against bias on the part of transcribers reported minimal improvements over a
period of intervention. What this meant as a practical matter was that in the studies where transcribers
were completely “blinded,” PCClist and PCCconv were not sensitive to differences in outcomes between
treatment groups and were possibly insensitive to changes over typical periods of therapy.
The purpose of the study reported here was to examine the sensitivity of several measures of
phonological improvement to changes during a relatively long period of intervention. This was a small
feasibility study for randomized controlled trial in which two interventions were compared. The
transcribers were completely blinded. Only the pre- and post-measures for the entire group of 13
children are reported here.
Method
Participants. The participants were 13 preschool-age children with phonological disorder who were
referred by USD 383 for Speech Groups, a joint project of the school district and the Speech and Hearing
Center. The project was approved by the K-State IRB and USD 383. The children were randomly
assigned to one of two treatments. All the children passed a hearing screening. None required
treatment for any concomitant disorder. Their mean age was 47.6 months (SD 6.79), their mean scaled
score on the PLS-4 was 106.8 (SD 14.27), and their median on the SHAPE was at the 5th percentile (range
2nd – 23rd).
The Assessments. Children were assessed at the beginning and end of 8 months of intervention while
producing a 137-word list and engaging in spontaneous conversation during play. The samples were
video-recorded using very high quality equipment. The measures were based on the video-recordings,
and they were made from transcripts generated by 5 transcribers in external sites who were completely
blinded to the children’s treatment group and to whether a sample was from the beginning or the end
of a period of intervention. Transcription reliability was assessed in several ways and was considered
adequate for these types of speech materials.
Consonant Acquisition Measures. Using a consonant acquisition measure that we devised, we
determined which consonants this group had not acquired at the beginning of treatment. We compared
them to two other lists of “late” and “difficult” consonants and determined that /v θ ð s z ʃ ʧ ʤ l r/ can
be considered Late and/or Difficult (L/D). In addition to the conventional PCC measures, we determined
the L/D PCC for the word lists and the conversations, as well as a measure of how many of the L/D
consonants had been acquired at the beginning and at the end of intervention.
Results
Table. Comparisons between the pre-treatment data and the post-treatment data for the whole group
of 13 participants. For all data reported as percentages, an arcsine data transformation was used.
Variable
Pre-treatment
mean (SD)
Post-treatment
mean (SD)
t-value
(related
pairs)
Probability Cohen’s
(p)
db
PCClist
64.9% (10.89%)
74.4% (9.06%)
3.991 (df=12)
.002
0.964
L/D PCClist
33.9% (12.64%)
48.9% (16.52%)
4.043 (df=12)
.002
1.00
Acquired L/D
consonants,
list
1.5 (0.97)
3.1 (1.38)
4.170 (df=12)
.001
1.290
PCCconv
67.3% (8.42%)
73.8% (8.97%)
2.640 (df=12a)
.022
0.745
L/D PCCconv
39.1% (14.26%)
53.4% (15.17%)
2.832 (df=11a)
.016
0.954
Acquired L/D
consonants,
conversation
2.9 (1.00)
4.2 (1.54)
3.218 (df=11a)
.008
1.023
a
Due to human error, no conversation was elicited from one of the children at Time 1. An estimated value was used for
comparisons involving PCCconv, but the child’s data were not used in the other analyses of conversational data.
b
Calculated using the formula for repeated measures presented by Robey, 2004, p. 315.
Findings and Discussion
This is a very small data set, with only 13 children. However, three findings may be relevant for future
research and practice:
• First, intervention periods longer than 4-5 months may be necessary for conventional PCC to
show changes. Over a period of 8 months, changes of 9.6-13.5% in conventional PCC can be
expected.
• Second, measures based on word lists and on Late/Difficult consonants appear to be more
sensitive to change over a period of intervention than measures based on conversations or on
the whole range of consonants.
• Three, L/D acquisition measures are probably numerically too small to be useful with children
who have moderate-to-severe PD due to floor effects. However, PCC for L/D consonants is likely
to be free of ceiling and floor effects.
Acknowledgements
This project was supported by grants from Kansas State University and from the College of
Human Ecology.
We thank staff of USD 383 for their assistance and cooperation with this study.
The parents and children who participated in the study have our deepest thanks, as do the
dedicated student clinicians and the many students who helped to analyze the data.
Many thanks to the 5 external transcribers whose contributions were so invaluable: Erica Bates,
Julie Erb, Fanisha Esfield, Sarah Moll, and Carly Thibault.
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