What is a Single Case Study Design? - Free Course on Thesis Proposal Writing (See Links Below)

TL;DR

A single case study design targets one case—an individual, group, or event—to produce an in-depth understanding of complex phenomena.

Briefing Cornell Notes

Briefing

A single case study design is a research method built to deliver a deep, detailed understanding of one “case”—an individual, a group, or an event—so researchers can map the complex dynamics that surround it. It’s widely used in psychology, social work, and education because it prioritizes rich, qualitative insight over broad measurement, making it especially useful for social and psychological phenomena that are hard to capture with quantitative methods alone.

The core strength of this approach is the ability to collect in-depth data from multiple sources while staying focused on one case. Researchers can draw on interviews, direct observation, and documentation (such as records or treatment plans) to build a comprehensive picture of what’s happening and why. That depth also supports theory-building: by examining the specific circumstances, relationships, and interactions within a single case, researchers can identify patterns and generate hypotheses that may later be tested in other contexts.

Another major payoff is the attention to uniqueness. Because the study centers on one case, it can highlight idiosyncratic factors—specific relationships, stressors, or supports—that might be averaged out in larger studies. Those findings can still be valuable beyond the case itself, particularly when the goal is to develop testable ideas about mechanisms (for example, how support systems influence coping).

The tradeoff is generalizability. Findings from a single case study may not apply to other cases because the results can be shaped by unique, non-replicable circumstances. That limitation matters when researchers want broad conclusions rather than contextual understanding. Even so, the design can still guide future research by pointing to what might matter and what should be examined more systematically.

A concrete example involves a family coping with a child who has a rare genetic disorder. Over several months, a researcher might interview family members, observe interactions, and review medical records and treatment plans. From that material, themes such as emotional stress and financial strain may emerge—alongside sources of support like extended family, support groups, and healthcare professionals. Those observations can lead to hypotheses about resilience, such as the role of social support, and can also suggest follow-up questions—like how different types of support affect coping or how financial stress changes coping strategies.

In psychology, the same logic can be applied to intervention evaluation. A researcher might study one individual undergoing cognitive behavioral therapy for depression, using interviews, observations, and self-report measures to track changes in mood, thoughts, and behaviors. The results can inform theories about how cognitive behavioral therapy works and generate hypotheses for later studies that test effectiveness more broadly.

Overall, the single case study design is a tool for producing detailed, context-rich insights and for developing hypotheses—best used when depth and mechanism matter more than statistical generalization.

Cornell Notes

A single case study design focuses research on one case—an individual, group, or event—to produce an in-depth understanding of complex real-world situations. It relies on detailed qualitative data gathered from multiple sources such as interviews, observation, and documentation, which helps researchers identify patterns, relationships, and key themes. The approach is especially useful in psychology, social work, and education when quantitative methods alone can’t capture the full complexity of social or psychological phenomena. Findings can generate insights and hypotheses that may be tested in future studies. Its main limitation is limited generalizability because results may depend on unique, idiosyncratic factors present in only that case.

What makes a single case study design different from other research approaches?

It centers on one case—such as a single person, a group, or an event—and aims for depth rather than breadth. By concentrating on one case, researchers can gather detailed qualitative information about specific circumstances, relationships, and dynamics. Data collection often combines interviews, observation, and documentation to build a comprehensive understanding of what’s happening within that single context.

Why is triangulating multiple data sources (interviews, observation, documents) important in this design?

Using multiple sources helps create a fuller picture of the case. Interviews can capture perspectives and experiences, observation can show how interactions unfold in real time, and documents (like medical records or treatment plans) provide factual context. Together, these sources support more credible pattern identification—such as recurring stressors, coping strategies, or changes over time.

How can a single case study contribute to theory-building and hypothesis generation?

By identifying themes and patterns unique to the case, researchers can propose explanations for what drives outcomes. For example, in a case involving a family coping with a child’s rare genetic disorder, the study might highlight emotional stress and financial strain while also pointing to support systems. From that, researchers can form hypotheses—such as the idea that social support plays a crucial role in coping—that can later be tested in broader research.

What is the main limitation of single case study findings?

Generalizability. Because the study focuses on one case, results may not apply to other cases. Unique or idiosyncratic factors—circumstances that don’t exist elsewhere—can strongly influence outcomes, making it difficult to draw broad conclusions beyond the studied context.

How would this design be used to evaluate a therapy like cognitive behavioral therapy?

A researcher could conduct a single case study on one individual receiving cognitive behavioral therapy for depression. Data might come from interviews, observations, and self-report measures to track changes in mood, thoughts, and behaviors. The results can then inform theories about the therapy’s potential effectiveness and generate hypotheses for future studies that test effectiveness more widely.

Review Questions

What kinds of data sources are typically used in a single case study, and what does each source contribute?
Give one example of how a single case study can generate a hypothesis, and explain why that hypothesis might be testable later.
What does limited generalizability mean in the context of single case study research, and how might it affect how results are interpreted?

Key Points

1
A single case study design targets one case—an individual, group, or event—to produce an in-depth understanding of complex phenomena.
2
Researchers typically collect detailed qualitative data from multiple sources, including interviews, observation, and documentation.
3
The design is especially useful in psychology, social work, and education when quantitative methods can’t capture key context and dynamics.
4
Single case studies can identify patterns and generate hypotheses that may be tested in other contexts.
5
Findings often highlight the uniqueness of a case by examining specific circumstances and relationships in detail.
6
The main limitation is limited generalizability because results may depend on unique, idiosyncratic factors not present in other cases.

Highlights

Single case studies trade statistical breadth for contextual depth by focusing on one case and collecting rich qualitative data.

Multiple data sources—interviews, observation, and documents—help build a comprehensive picture of what’s happening.

Even when generalization is limited, the approach can still generate hypotheses by revealing mechanisms and patterns within the case.

A family coping with a rare genetic disorder can be studied over months using interviews, observation, and medical records to identify stressors, supports, and coping factors.

In therapy research, one person’s response to cognitive behavioral therapy can be tracked through interviews, observations, and self-report measures to inform future testing.

Topics

Single Case Study Design
Qualitative Research
Case-Based Hypothesis Generation
Generalizability
Therapy Evaluation