Single Case Experimental Designs (SCEDs) are a rigorous methodological approach for evaluating interventions at the individual level. They allow researchers and clinicians to establish causal relationships through systematic manipulation of variables within a single individual (or small group). SCEDs are particularly useful in fields where large-scale randomised controlled trials (RCTs) are impractical, such as personalised medicine, behavioural sciences, and rehabilitation. By incorporating repeated outcome measurements over time, during intervention and non-intervention phases, SCEDs provide statistically and clinically meaningful data.
Key Features of a Single Case Experimental Design
SCEDs rely on structured phases to systematically assess the effect of an intervention. The most common designs include AB, ABA, and multiple baseline design. In an AB design, a baseline phase (A) is followed by an intervention phase (B). The ABA design reintroduces the baseline phase after the intervention to examine whether the effects persist or return to baseline levels.Multiple baseline designs stagger the timing of the introduction of the intervention across individuals (or across behaviours within the same individual) to demonstrate that changes are linked to the intervention rather than other factors. Data is collected frequently and in a structured manner, allowing for precise tracking of changes over time and confidence in the observed effects. The use of visual analysis, along with statistical methods such as dynamic regression modeling and effect size calculations, improves the interpretation of results by identifying patterns, trends, and the magnitude of intervention effects.
Another key feature of SCEDs is the ability to assess intervention generalisation and maintenance. Investigators can evaluate whether the effects of an intervention persist after its withdrawal or extend beyond the specific conditions under which it was applied. This is particularly relevant in behavioural and clinical research, where long-term efficacy and adaptability to different environments are critical. Beyond within-individual effects, replication across individuals is essential for establishing the reliability of findings. Unlike group-based designs that rely on aggregation, SCEDs validate effects through repeated testing within and across individuals, reducing the likelihood that observed changes are due to chance, maturation (i.e. natural changes that occur in an individual over time), or external influences. Design modifications such as randomisation, counterbalancing, and multiple baseline approaches further enhance internal validity and mitigate potential biases.
Single-case experimental designs (SCEDs) are widely used in medicine, psychology, and allied health to assess how well an intervention works for an individual. Unlike randomised controlled trials (RCTs), which provide group-level averages, SCEDs focus on personal responses. This is especially useful for conditions that vary between individuals, such as chronic pain, neurological disorders, and mental health conditions.
For medical devices, SCEDs offer a structured way to evaluate performance, particularly when customisation is needed. The Haute Autorité de Santé (2021) discusses their role in medical device trials, emphasising their value in cases where large-scale studies are impractical (p. 32, methodology guide).
Why SCEDs Are Useful
Workable with Small Populations
SCEDs need fewer participants, making them practical when large trials aren’t possible or ethical. This applies to rare diseases, paediatrics, and cases where withholding treatment isn’t an option.
Better Fit for Clinical Practice
Rather than controlled lab settings, SCEDs focus on real-world use, making findings more relevant to patient care. Instead of generalising across a group, they provide results directly applicable to the individual.
Flexible and Adaptable
SCEDs allow adjustments during the study without losing validity. This is particularly useful in digital therapeutics and MedTech, where interventions can change based on user data. Continuous outcome tracking provides detailed information on how treatments are working.
Lower Cost, Fewer Logistics
Traditional trials require large teams, long timelines, and extensive funding. SCEDs can be done with fewer resources while still maintaining scientific rigour, making them an attractive option for research groups, startups, and institutions with limited budgets.
Applications of Single Case Design
SCEDs are widely applied in fields that require individualised treatment evaluation. Unlike traditional group-based studies, they track how interventions work for a single person, making them useful in areas where responses vary.
Medicine & Pharmaceuticals
SCEDs can help fine-tune medication regimens by assessing how individuals respond to specific dosages. This is particularly relevant in chronic pain management, oncology, and cases where standardised dosing may not be effective or intervention half-lives are unknown or onset/offset are slow. They can be particularly useful for rare diseases and in early phases of drug development.
Complementary Medicine
SCEDs provide a way to evaluate treatments with variable responses, unknown half-lives, or complex compound mixtures. They are used to assess the effectiveness of herbal remedies, acupuncture, and other non-conventional therapies where traditional study designs may fall short.
Digital Health & MedTech
SCEDs play a role in refining adaptive interventions, such as cognitive-behavioural therapy apps and biofeedback systems. MedTech companies use SCEDs to test and optimise medical devices, ensuring they work effectively for individuals before broader commercialisation.
Medical Cannabis
SCEDs can be used to determine optimal dosing, track side effect profiles, and assess the effectiveness of different cannabis strains for individual patients. Given the variability in response, this approach helps personalise treatment plans.
Rehabilitation & Behavioural Research
SCEDs are widely used in rehabilitation sciences, where treatment success depends on individual progress. They support personalised approaches in physiotherapy, speech therapy, and neurorehabilitation, ensuring interventions are adjusted as needed.
The ability to establish causal relationships without requiring extensive participant recruitment makes SCEDs a valuable tool across multiple disciplines. Their methodological rigour, combined with practical applicability, ensures that findings are both scientifically valid and directly relevant to clinical decision-making.
Ready to get started?
While SCEDs offer significant benefits, they also present challenges that require careful attention. Designing and conducting an SCED demands detailed planning, particularly in managing the logistics of data collection and analysis. This process can be time-consuming, involving the development of clear protocols, ensuring participant adherence, and maintaining consistent outcome reporting. Analysing SCED data requires specialised statistical knowledge, and without experience, accurate interpretation can be challenging. Access to professionals skilled in SCEDs is essential for successful outcomes.
At N-of-1 Hub, we provide expert guidance and training to help you navigate these complexities. Whether you're a university researcher, clinician, or part of an organisation conducting clinical trials - be it pharmaceuticals, complementary medicines, medical devices, or medical cannabis - we offer the expertise needed to design, conduct, and analyse Single Case Experimental Designs. Our courses are also ideal for health professionals, such as medical practitioners, physiotherapists, naturopaths, psychologists, dietitians and naturopaths, looking to implement more personalised care and improve patient outcomes.
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