Maas & Farinella (2012)

Single Subject Designs



1. The summary of the intervention procedure(s) can be viewed by scrolling about two-thirds of the way down on this page.

2. Key:

C = clinician

CAS = childhood apraxia of speech

CNT = could not test

DTTC = Dynamic Temporal and Tactile Cueing

ES = effect size

NA = not applicable

P = participant or patient

S = strong syllable

SLP = speech=language pathologist

w = weak syllable

WNL = within normal limits


SOURCE: Maas, E., & Farinella, K. A. (2012). Random versus blocked practice in treatment for childhood apraxia of speech. Language, Speech, and Hearing Services in Schools, 55, 561-578.




DATE: August 8, 2014



TAKE AWAY: The focus of these single subject experimental design investigations was to determine if there was an advantage for blocked versus random practice for children with childhood apraxia of speech (CAS). The investigation is relevant to this blog because the intervention involved the manipulation of rate. The investigators included a thorough description of the participants (Ps), intervention, and scoring of P responses to treatment conventions. The intervention was judged to be effective for 3 of the 4 Ps but the results regarding the practice schedule were equivocal.


  1. What was the focus of the research? Clinical Research



  1. What type of evidence was identified?

a. What type of single subject design was used? Single Subject Experimental Design with Specific Clients- Alternating Treatments Design with Multiple Baselines across Behaviors


b. What was the level of support associated with the type of evidence?

Level = A                                                         



  1. Was phase of treatment concealed?

a. from participants? No

b. from clinicians? No

c. from data analyzers? Yes



  1. Were the participants adequately described? Yes

a. How many participants were involved in the study? List here: 4


b. The following characteristics were described:

  • age: 5;0 to 7;9
  • gender: 2m; 2f
  • expressive language: moderate delay (2); severe delay (1); could not test (CNT, 1)
  • receptive language: within normal limits (WNL, 2); low- average (1); mild-moderate delay (1)
  • language spoken: all monolingual English speakers
  • Hearing: all WNL
  • Medical/neurological diagnosis: none had diagnoses at the time of the investigation
  • motor skills: limited manual motor skills (1); history of hypotonia and gross/fine motor delay (1)
  • sensory processing skills: impaired (1)


c. Were the communication problems adequately described? Yes

  • The disorder type was CAS
  • Other aspects of communication that were described for each of the Ps:


  • inconsistent vowel/consonant substitutions/distortions
  • segmented speech
  • intermittent hypernasality
  • equal and incorrect stress in multisyllabic words
  • reduced intelligibility
  • inconsistent phonological patterns


  • inconsistent vowel/consonant errors
  • articulatory groping
  • intermittent hypernasality
  • breathy/harsh voice quality
  • stereotypical nonword utterance
  • mild left facial asymmetry
  • possible mild unilateral upper motor neuron dysarthria


  • moderate-severe dysarthria (mixed spastic-flaccid)
  • inconsistent consonants/vowels errors
  • speech sound and syllable segmentation
  • intermittent hypernasality
  • intermittent hoarse/breathy voice quality
  • weakness of the tongue
  • prosodic abnormalities (incorrect and equal stress, reduced speech rate)


  • prosodic abnormalities (incorrect and excessive stress, segmentation of syllables)
  • occasional speech sound distortions and vowel errors were occasionally observed


  1. Was membership in treatment maintained throughout the study? Yes

a. If there was more than one participant, did at least 80% of the participants remain in the study? Yes

b. Were any data removed from the study? No



  1. Did the design include appropriate controls? Yes

a. Were baseline collected on all behaviors? Yes

b. Did probes include untrained data? Yes

c. Did probes include trained data? Yes

d. Was the data collection continuous? No

e. Were different treatment counterbalanced or randomized? Yes

  1. f. Was treatment counterbalanced or randomized? Randomized?



  1. Were the outcomes measure appropriate and meaningful? Yes

a. The outcome:

OUTCOME #1*: Improved accuracy (speech sound, lexical stress, segmentation/concordance) on target probes

* The investigators designed separate word lists for each P, taking into consideration speech sound error profiles. The following were the targets:

– initial cluster

– 2 syllable words

– 3 syllable words

– final clusters

– final fricative

– final liquids

– initial fricatives

– initial liquids

– 4 syllable Strong-Weak-Strong-Weak (SwSw) words

– 4 syllable wSwS words

– 3 syllable wSw words

– 3 syllable Sww words

b. The outcome was subjective.

c. The outcomes was not objective.                                            

d. The investigators provided outcome reliability data.

e.  The mean interrater reliability ranged from 79% to 87%.


  1. Results:
  2. Did the target behavior improve when it was treated? Inconsistent
  3. b.   For

OUTCOME #1: Improved accuracy (speech sound, lexical stress, segmentation/concordance) on target probes —The overall quality of improvement was moderate

– P1, P3, P4 –improved **

– P2 did not improve

(**NOTE–The findings regarding the relative effectiveness of the practice schedule were equivocal; 2Ps exhibited stronger progress for the blocked schedule and 1P exhibited stronger progress with the random schedule.)

  1. Description of baseline:
  2. Were baseline data provided? Yes

OUTCOME #1: Improved accuracy (speech sound, lexical stress, segmentation/concordance) on target probes – 3 data points


  1. Was baseline low and stable? (The numbers should match the numbers in item 7a.)

OUTCOME #1: For the most part, baseline was low (the highest percentage correct of a target during baseline was approximately 35%) and moderately stable.


c & d. What was the percentage of nonoverlapping data (PND)?

OUTCOME #1: Improved accuracy (speech sound, lexical stress, segmentation/concordance) on target probe

  • P1 – PND was 75% to 100% (fairly to highly effective)
  • P2 – PND was 0% for all targets (ineffective)
  • P3 – PND was 0% to 75% (ineffective to fairly effective)
  • P4 – PND was 0% to 50% (ineffective to questionable effectiveness)



  1. What was the magnitude of the treatment effect.”


NOTE: The investigators used an effect size (ES) of 1.00 or more as evidence of effectiveness (p. 567); there was no gradation for effectiveness.

OUTCOME #1: Improved accuracy (speech sound, lexical stress, segmentation/concordance) on target probe

  • P1 – ES was 3.55 (random) and 4.04 (block)
  • P2 – ES was 0.62 (blocked); random could not be calculated because of zero variance.
  • P3 – ES was 3.16 (random) and 1.50 (block)
  • P4 – ES was 1.31 (random) and 1.69 (block)


  1. Was information about treatment fidelity adequate? Yes. Treatment fidelity ranged from 61% to 88%. One P was associated with percentages ranging from 61% to 71%. All other Ps had percentages of 75% or above.



  1. Were maintenance data reported? Yes. There were multiple specific targets for each of the Ps. Although there were some exceptions, for the most part, Ps did not maintain their gains in therapy at a follow-up session one month after termination of the investigation.



  1. Were generalization data reported? Yes Generalization varied; overall should be described as limited.








PURPOSE: To improve motor speech learning

POPULATION: Childhood Apraxia of Speech; Child







DOSAGE: 3 times a week,


ADMINISTRATOR: SLP or a graduate clinician


STIMULI: visual stimuli (index cards—10 of each target), auditory stimuli, tactile cues



  • The investigators use Dynamic Temporal and Tactile Cueing (DTTC) as a treatment but they compared using random and blocked practice schedules for their investigation.
  • DTTC includes motor learning, modeling, integral stimulation, drill, focus on core vocabulary, rate reduction, variation in gap between C’s model and P’s attempt, tactile cues, reinforcement, and variation in feedback schedule.
  • Blocked Practice = index cards for the same word were practiced together and then C moved on to the next word
  • Random Practice = C shuffled the all the cards that were to be used for that day’s session


  • C provided verbal feedback to P only 60% of the time
  • Steps in DCCT

1. C directs P “Watch me, listen carefully, and repeat after me” (p. 577). C then produces the target word on the index card.

2. When P is correct, C waits 2 to 3 seconds, and either

– provides feedback (60% of the time) and reinforces C tangibly (e.g., stickers or bubbles) and

– goes to the next word.

3. When P is incorrect,

– during feedback trials (60% of the time)

  • C waits 2- 3 seconds
  • C notes that the production was not accurate and describes how it was inaccurate
  • up to 2 times, C and P slowly and simultaneously produce the target word
  • C then fades support by only mouthing the target word during an attempt to produce it
  • C produces the word and P immediately imitates it
  • C waits 2 to 3 seconds before providing feedback

– during No Feedback trials (40% of the time)

  • C waits 2- 3 seconds
  • up to 2 times, C and P slowly and simultaneously produce the target word
  • C then fades support by only mouthing the target word during an attempt to produce it
  • C produces the word and P immediately imitates it
  • C waits 2 to 3 seconds and then says “Now let’s do another one” (p. 577).

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