Single-case Experimental Design Studies Research Articles

Fine-grained effect sizes.

To make transparent individuals' responses to intervention over time in the systematic review of single-case experimental designs, we developed a method of estimating and graphing fine-grained effect sizes. Fine-grained effect sizes are both case- and time-specific and thus provide more nuanced information than effect size estimates that average effects across time, across cases, or both. We demonstrate the method for estimating fine-grained effect sizes under three different baseline stability assumptions: outcome stability, level stability, and trend stability. We then use the method to graph individual effect trajectories from three single-case experimental design studies that examined the impact of self-management interventions on students identified with autism. We conclude by discussing limitations associated with estimating and graphing fine-grained effect sizes and directions for further development. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The interest to expand group-based studies with single-case experimental design studies in the investigation of the effects of physical exercise in frail older adults: an opinion article.

The interest to expand group-based studies with single-case experimental design studies in the investigation of the effects of physical exercise in frail older adults: an opinion article.

Comparing Interventions With Speech-Generating Devices and Other Augmentative and Alternative Communication Modes: A Meta-Analysis.

Optimal augmentative and alternative communication (AAC) systems for children with complex communication needs depend in part on child characteristics, child preferences, and features of the systems themselves. The purpose of this meta-analysis was to describe and synthesize single case design studies comparing young children's acquisition of communication skills with speech-generating devices (SGDs) and other AAC modes. A systematic search of published and gray literature was conducted. Data related to study details, rigor, participant characteristics, design information, and outcomes were coded for each study. A random effects multilevel meta-analysis was performed using log response ratios as effect sizes. Nineteen single case experimental design studies with 66 participants (M age = 4.9 years) met inclusion criteria. All but one study featured requesting as the primary dependent variable. Visual analysis and meta-analysis indicated no differences between use of SGDs and picture exchange for children learning to request. Children demonstrated preferences for and learned to request more successfully with SGDs than with manual sign. Children who preferred picture exchange also learned to request more easily with picture exchange than with SGDs. Young children with disabilities may be able to request equally well with SGDs and picture exchange systems in structured contexts. More research is needed comparing AAC modes with diverse participants, communication functions, linguistic complexity, and learning contexts. https://doi.org/10.23641/asha.22111181.

Examining the normality assumption of a design-comparable effect size in single-case designs.

What Works Clearinghouse (WWC, 2022) recommends a design-comparable effect size (D-CES; i.e., gAB) to gauge an intervention in single-case experimental design (SCED) studies, or to synthesize findings in meta-analysis. So far, no research has examined gAB's performance under non-normal distributions. This study expanded Pustejovsky et al.(2014) to investigate the impact of data distributions, number of cases (m), number of measurements (N), within-case reliability or intra-class correlation (ρ), ratio of variance components (λ), and autocorrelation (ϕ) on gAB in multiple-baseline (MB) design. The performance of gAB was assessed by relative bias (RB), relative bias of variance (RBV), MSE, and coverage rate of 95% CIs (CR). Findings revealed that gAB was unbiased even under non-normal distributions. gAB's variance was generally overestimated, and its 95% CI was over-covered, especially when distributions were normal or nearly normal combined with small m and N. Large imprecision of gAB occurred when m was small and ρ was large. According to the ANOVA results,data distributions contributed to approximately 49% of variance in RB and 25% of variance in both RBV and CR. m and ρ each contributed to 34% of variance in MSE. We recommend gAB for MB studies and meta-analysis with N ≥ 16 and when either (1) data distributions are normal or nearly normal, m = 6, and ρ = 0.6 or 0.8, or (2) data distributions are mildly or moderately non-normal, m ≥ 4, and ρ = 0.2, 0.4, or 0.6. The paper concludes with a discussion of gAB's applicability and design-comparability, and sound reporting practices of ES indices.

Effects of Explicit Vocabulary Interventions for Preschoolers: An Exploratory Application of the Percent of Goal Obtained Effect Size Metric.

Systematic reviews of literature are routinely conducted to identify practices that are effective in addressing educational and clinical problems. One complication, however, is how best to combine data from both group experimental design (GED) studies and single-case experimental design (SCED) studies. Percent of Goal Obtained (PoGO) has been developed as a metric to express the size of the effect relative to the distance to a goal, which could have broad applicability. This study sought to augment this descriptive index with estimates of standard errors, which are needed to use PoGO as an effect size metric in meta-analyses of SCED and GED studies. This study investigated the application of PoGO and standard errors to both SCED and GED studies examining a common intervention approach used with a single population. Sixteen articles investigating explicit vocabulary instruction applied to pre-K and kindergarten students were identified. PoGO and standard errors were calculated for variations of explicit vocabulary interventions. Evaluated interventions included six studies using exclusively an SCED, nine studies using a GED, and one that used both. PoGO was calculated for each treatment condition when applicable (i.e., alternating treatments designs). Standard errors and confidence interval limits also were calculated. PoGO effect size values ranged from 14.4% to 93.6%. PoGO for single-case experiments was 49.2% with a standard error of 7.26, and for group experiments, it was 30.8% with a standard error of 3.71. Despite variation in the percentage of goal obtained across studies, the high degree of overlap in PoGO and standard errors between single-case and group experiments provides an indication that systematic reviews can apply this effect size metric to combine information obtained across experimental designs.

Evaluating the design and evidence of single-case experimental designs using the What Works Clearinghouse standards

In 2020, the What Works Clearinghouse (WWC) for single-case experimental design (SCED) studies released an updated version of their standards and procedures handbook (Version 4.1). Because of these updates, there is a need to understand the implications for the field in terms of quality rating of the design, and subsequent synthesis of evidence at the study and meta-analytic level. This study provides a comparison between the previous SCED design and evidence standards, and the updated ones published in 2020 as Version 4.1. We are interested in whether Version 4.1 results in differences in terms of (1) quality rating of the design and (2) analysis and meta-analysis of research evidence. The results indicate no differences related to quality rating of the design, but there are notable differences in terms of how evidence is analyzed, synthesized, and reported. This is further illustrated using a selected publication, namely Pivotal Response Training in which research evidence is meta-analyzed related to the effectiveness of Pivotal Response Training as an intervention to increase communication of children (aged 2–18) with autism. Based on the findings, recommendations and implications are discussed.

The Relationship Between Visual Depictions of Rate of Improvement and Quantitative Effect Sizes in Academic Single-Case Experimental Design Studies

The Relationship Between Visual Depictions of Rate of Improvement and Quantitative Effect Sizes in Academic Single-Case Experimental Design Studies

Single-Case Writing Interventions for Students with Disorders of Intellectual Development: A Systematic Review and Meta-Analysis

Students with disorders of intellectual development (ID) often experience writing difficulties, and effective interventions are highly needed. This systematic review and meta-analysis of single-case experimental design (SCED) studies summarize the effects of writing interventions for students with disorders of ID aged 4–19 years. We conducted a systematic search of seven databases, ancestral and forward searches of relevant sources, and contacted well-known authors in the field. Fifteen and 10 studies were included in the systematic review and meta-analyses, respectively. The overall results indicate that the participants improved their writing skills, with a large between-case standardized mean difference (BC-SMD) effect on the number of words and sentences written (BC-SMD = 1.22) and on the quality of paragraph and story writing (BC-SMD = 1.39). Students with disorders of ID can benefit from writing interventions, and the study results may provide practitioners with important insight into promising writing instructions and materials. There is a need for high-quality research targeting encoding (i.e., transforming sound into letters) skills for early school-age students with disorders of ID.

The effectiveness of aerobic versus strengthening exercise therapy in individuals with chronic whiplash-associated disorder: a randomised single case experimental design study

Purpose Recent RCTs and meta-analyses compare the effectiveness of different types of exercise for chronic whiplash associated disorder (WAD). This study aimed to verify whether the results of these studies translate to statistically significant and clinically meaningful effects in individual participants. Materials and methods A series of replicated randomised single case experimental design studies (SCEDs) with A-B design (A: baseline, B: intervention). Eight participants with chronic WAD (8 female, mean [SD] age 47 [10] years) were randomised into one of four baseline durations (5, 8, 11, and 14 days) and to one of two eight-week exercise interventions (aerobic or strengthening). Daily measures of pain intensity, bothersomeness, and interference were collected during the baseline phase and the intervention phase. Results Visual analyses indicated that three participants in the aerobic exercise group meaningfully improved. No improvements were found in the strengthening group. Effect sizes favoured the aerobic exercise group, yet randomisation tests of pooled effects did not show a difference in between-intervention effectiveness. Conclusion Contrary to our expectations, three out of four participants were nearly pain-free at the end of the aerobic exercise intervention, whereas none of the participants in the strengthening group improved meaningfully. This suggests that aerobic exercise may be favourable for WAD. Implications for Rehabilitation Our results suggest that aerobic exercises are favourable over strengthening exercises and may be the preferred option for patients with chronic WAD. We found substantial variability in self-reported outcomes within participants, clinicians should be aware of this in the judgement of treatment effectiveness.

Effects of Interventions Involving Speech Output Technologies on Communication Outcomes for Individuals With Developmental Disabilities: A Scoping Review.

This scoping review aimed to map the literature on the effects of interventions involving speech output technologies on communication outcomes for individuals with developmental disabilities other than autism spectrum disorder. A scoping review methodology was used to limit bias in searching, selecting, coding, and synthesizing relevant intervention studies. This involved a multifaceted search for studies conducted between 1991 and March 2021 using various electronic databases, ancestry searches, and forward citation searches from selected articles. Studies had to meet stringent inclusion criteria. Each study was summarized in terms of authors, purpose, participants, design, speech output, outcomes, effectiveness, and quality appraisal. Twenty-five single-case experimental design studies (88 participants) and one group design studies (62 participants) qualified for inclusion. Most of the participants had multiple diagnoses followed by a diagnosis of cerebral palsy and Down syndrome. Most studies focused on requesting behaviors and to a much lesser extent on syntactic structure and word identification. A dearth of high-quality studies was identified. Overall, there is a paucity of high-quality research investigating the effects of speech output technologies for children with developmental disabilities. Additionally, several directions for future research are posited. https://doi.org/10.23641/asha.20468928.

Effectiveness of Interventions for English Learners with Word Reading Difficulties: A Research Synthesis

AbstractThis study meta‐analyzed the last four decades (1980–2020) of reading intervention research focused on improving reading outcomes for English language (EL) students in Grades K–5 with or at risk for word reading difficulties. Experimental and quasi‐experimental group design and single‐case experimental design (SCED) studies were included; 10 group design and 7 SCED studies met inclusion criteria (m = 61; total student N = 2,270). Visual inspection of the effect size distribution revealed that the assumption of between‐study heterogeneity was not supported; therefore, the findings were synthesized for SCED studies separately from those reported in group design studies. Implications for practice, policy, and future research are discussed.

Statistical Power of Piecewise Regression Analyses of Single-Case Experimental Studies Addressing Behavior Problems

In intervention research, single-case experimental designs are an important way to gain insights into the causes of individual changes that yield high internal validity. They are commonly applied to examine the effectiveness of classroom-based interventions to reduce problem behavior in schools. At the same time, there is no consensus on good design characteristics of single-case experimental designs when dealing with behavioral problems in schools. Moreover, specific challenges arise concerning appropriate approaches to analyzing behavioral data. Our study addresses the interplay between the test power of piecewise regression analysis and important design specifications of single-case research designs. Here, we focus on the influence of the following specifications of single-case research designs: number of measurement times, the initial frequency of the behavior, intervention effect, and data trend. We conducted a Monte-Carlo study. First, simulated datasets were created with specific design conditions based on reviews of published single-case intervention studies. Following, data were analyzed using piecewise Poisson-regression models, and the influence of specific design specifications on the test power was investigated. Our results indicate that piecewise regressions have a high potential of adequately identifying the effects of interventions for single-case studies. At the same time, test power is strongly related to the specific design specifications of the single-case study: Few measurement times, especially in phase A, and low initial frequencies of the behavior make it impossible to detect even large intervention effects. Research designs with a high number of measurement times show robust power. The insights gained are highly relevant for researchers in the field, as decisions during the early stage of conceptualizing and planning single-case experimental design studies may impact the chance to identify an existing intervention effect during the research process correctly.

A systematic review of single-case experimental design meta-analyses: characteristics of study designs, data, and analyses

Given the increasing interest in meta-analyses of Single-Case Experimental Design (SCED) studies mainly in the fields of behavioral, communication disorders, educational, and rehabilitation research, the aim of the present review is to determine the general characteristics of these meta-analyses, namely design characteristics, the kind of data provided in the primary studies and the ones included in meta-analyses, and the type of analyses that were conducted. In this review, 178 meta-analyses were examined for these characteristics. The results indicate that the number of SCED meta-analyses has increased remarkably in recent years. The most frequently used effect size metric was the percentage of non-overlapping data (PND) and the most commonly utilized analysis for synthesizing the results of primary SCEDs was a simple average of effect sizes. The current study provides insights in the characteristics of primary SCED studies and SCED meta-analyses, and therefore can help in further developing methodological techniques and in evaluating whether the currently used techniques are in line with the methodological advancements.

Brief and Telehealth Acceptance and Commitment Therapy (ACT) Interventions for Stress in Inflammatory Bowel Disease (IBD): A Series of Single Case Experimental Design (SCED) Studies.

Psychological intervention targeting distress is now considered an integral component of inflammatory bowel disease (IBD) management. However, significant barriers to access exist which necessitate the development of effective, economic, and accessible brief and remote interventions. Acceptance and commitment therapy (ACT) is a therapy with demonstrated acceptability and a growing evidence base for the treatment of distress in IBD populations. The present paper trialled two brief ACT interventions via randomized multiple baseline designs. Study 1 trialled a single-session ACT intervention (delivered face-to-face and lasting approximately two hours) targeting stress and experiential avoidance, respectively. Participants were seven people with an IBD diagnosis who presented with moderate to extremely severe stress (five females, two males; M age = 39.57, SD = 5.74). The findings of study 1 indicate that a single-session ACT intervention represented an insufficient dosage to reduce stress and experiential avoidance. Study 2 investigated a brief telehealth ACT intervention (delivered via a video conferencing platform and lasting approximately four hours) targeting stress and increased psychological flexibility. Participants (N = 12 people with an IBD diagnosis and mild to extremely severe stress) completed baselines lasting from 21 to 66 days before receiving a two-session ACT telehealth intervention supplemented by a workbook and phone consultation. Approximately half of participants experienced reduced stress, increased engagement in valued action, and increased functioning. Despite shortcomings such as missing data and the context of COVID-19, the present findings suggest that brief ACT interventions in this population may be effective and economic, though further research and replications are necessary.

Training Individuals to Implement Discrete Trials with Fidelity: A Meta-Analysis

Discrete trial training is a popular teaching method for individuals with autism, but it is not easily implemented with fidelity due to its complexity. This is the first meta-analysis of single-case experimental design studies to quantify the impact of behavioral skills training on individuals’ ability to implement discrete trials with fidelity. Furthermore, this meta-analysis examines the four training methods that make up behavioral skills training—feedback, instruction, modeling, and rehearsal—to determine the “active ingredients” of behavioral skills training. A total of 46 single-case experimental design studies are included in this meta-analysis. Hierarchical linear modeling, which has the ability to analyze clustered data, is the meta-analytic technique used to estimate the effectiveness of behavioral skills training across studies. Results show that behavioral skills training has a statistically significant positive effect on discrete trial training implementation fidelity; therefore, behavior skills training is recommended for discrete trial training implementation instruction.

On the role of operant contingencies in the maintenance of inappropriate mealtime behavior: An epidemiological analysis.

Functional analysis is the primary assessment used to determine the function of inappropriate mealtime behavior in children with feeding disorders. Based on single-case experimental design studies and recent reviews, the prevalence of negative reinforcement alone in the maintenance of inappropriate mealtime behavior appears to be much greater than positive reinforcement alone. We conducted a retrospective consecutive-controlled case series to determine the generality of previous findings. Results of the epidemiological analysis support prior research in that negative reinforcement in the form of escape (44.8%), and multiple control (i.e., positive and negative reinforcement) in the forms of escape and attention (37.2%), are considerably more prevalent than positive reinforcement alone (2.5%). We discuss the relationship between functional analysis of inappropriate mealtime behavior and treatment utility. Further, we describe avenues of future research designed to advance the application of functional analysis in feeding disorders beyond inappropriate mealtime behavior.

Narrative intervention in school-aged children with autism spectrum disorder: a systematic review

ABSTRACT This review evaluated the evidence for narrative intervention on language and pragmatic outcomes for school-aged children with autism spectrum disorder (ASD). The study protocol for this review followed the PRISMA-Protocol checklist and was pre-registered on Open Science Framework. Ten electronic databases were searched to identify experimental designs studies that targeted school-aged children aged 5–18 with ASD. Two independent reviewers evaluated the inclusion eligibility of full-text studies. All included studies were critically appraised by two independent reviewers. Data were coded for study characteristics and outcomes of interest. Results from different outcome measures were synthesized qualitatively. The report was reviewed with the PRISMA checklist to ensure complete reporting. Forty participants from seven studies were included in this review. Six single-case experimental design studies and one group study were included. All these studies included methodological flaws that reduced the strength of evidence. The results indicated that narrative intervention might have large effects on comprehension of discourse, medium effects on production of macrostructure and microstructure, and small effects on pragmatic skills compared to pretreatment. For maintenance effects and other outcome constructs, including pragmatic skills, it was inconclusive whether the narrative intervention had true effects. Evidence from this review suggests that narrative intervention may produce medium-size effects on several constructs of language outcomes. Nonetheless, there was no evidence that showed those gains could be maintained post-treatment. The methodological weaknesses and the small sample of included studies restrict stronger conclusions from being drawn. More high-quality group studies with clearly described treatment procedures are needed.

Shared Interactive Book Reading Interventions for Young Children With Disabilities: A Systematic Review

Purpose Shared interactive book reading (SIBR) is an evidence-based practice for young children who are typically developing and those with developmental disabilities or considered at risk for developmental delays. The purpose of this review was to provide a comprehensive examination of the evidence of using SIBR to facilitate growth in language skills for young children with developmental disabilities and/or delays. Specifically, authors examined the descriptive characteristics, study rigor, and effect sizes for language and literacy outcomes. Method We extracted data from studies meeting specified criteria (n = 23) published in peer-reviewed journals on a wide range of variables, including participant characteristics, setting, training/coaching, defined independent and dependent variables, study rigor, and overall outcomes. Descriptive and study rigor data were aggregated using descriptive statistics. Effect-size estimates were calculated for all child outcomes related to language. Results Descriptive data were variable across studies. Three single-case experimental design and three group design studies met design standards without reservations. Single-case experimental design studies overall showed positive effects on child language and communication. Within group design studies, expressive language outcomes showed the largest effect sizes. Conclusion A review of SIBR studies indicates this as a viable intervention to positively impact the language skills of young children with developmental disabilities and/or delays. Supplemental Material https://doi.org/10.23641/asha.16674355.

The Power to Explain Variability in Intervention Effectiveness in Single-Case Research Using Hierarchical Linear Modeling.

This study investigated the power of two-level hierarchical linear modeling (HLM) to explain variability in intervention effectiveness between participants in context of single-case experimental design (SCED) research. HLM is a flexible technique that allows the inclusion of participant characteristics (e.g., age, gender, and disability types) as moderators, and as such supplements visual analysis findings. First, this study empirically investigated the power to estimate intervention and moderator effects using Monte Carlo simulation techniques. The results indicate that larger values for the true effects and the number of participants resulted in a higher power. The more moderators added to the model, the more participants needed to detect the effects with sufficient power (i.e., power ≥.80). When a model includes three moderators, at least 20 participants are required to capture the intervention effect and moderator effects with sufficient power. For that same condition, but only including one moderator, seven participants are sufficient. Specific recommendations for designing a SCED study with sufficient power to estimate intervention and moderator effects were provided. Second, this study introduced a newly developed user-friendly point and click Shiny tool, PowerSCED. This tool assists applied SCED researchers in designing a SCED study that has sufficient power to detect intervention and moderator effects. To end, the use of HLM with the inclusion of moderators was demonstrated using two previously published SCED studies in the journal School Psychology Quarterly.

Effects of Writing Interventions on the Level and Trend of Total Words Written: A Meta-Analysis

We estimated effects of writing interventions on the level and trend of writing fluency—rate of total words written over time—by students with and without disabilities. Using mixed-effects regression and an information-theoretic ranking of competing models, we synthesized results of 42 single-case experimental design studies with a total of 205 students. A variety of acquisition and fluency interventions were used across studies, such as self-regulated strategy development and timed practice with performance feedback. We found acquisition and fluency interventions produced an increase in level and a gradual increase in trend of total words written per minute. Students receiving fluency intervention tended to have higher levels of performance across experimental phases (i.e., baseline, intervention, and postintervention), but students receiving acquisition had steeper upward trends. In addition, we found higher levels of total words written per minute on writing tasks with brief time limits (i.e., ≤10 min) and in the writing of older students.