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Assignment questions
Social workDiscussion postPractice evaluation

Choosing and Using Single-System Design

The prompt builds its own case: you cannot control a person's life the way you control an experiment. Single-system design is the answer it proposes, and it has real limits.

Editorial process

Last reviewed · August 16, 2026

01

The human element is the whole difficulty

The prompt spends its whole setup on one problem: as soon as a human element enters, causal inference gets hard, because clients implement interventions outside the practitioner's observation and nobody can exert total control over another person's life. Single-system design is offered as the response, so present it as one. Its logic is to use the client as their own control: measure a target behaviour repeatedly during a baseline phase, introduce the intervention, keep measuring, and read the change in level, trend and variability across the phase boundary. That is why the notation matters — an AB design is the basic form, ABA withdraws the intervention, ABAB reintroduces it, and a multiple baseline staggers introduction across behaviours or settings, which is how you get stronger causal evidence without withdrawing something that is helping. Say which variant you would use and what the case would have to look like for the next one up.

The measurement decisions are where practice usually breaks down, so be concrete. The target has to be defined so that two observers would count it the same way — 'anxiety' is not measurable, 'panic episodes lasting more than five minutes' is. The baseline has to be long enough to show a trend, and a baseline already improving is the most common reason a later gain cannot be attributed to anything. Then be honest about the limits, because they are the reason this design is a compromise rather than a solution. It cannot rule out history and maturation the way a controlled trial can; the practitioner is usually both the intervener and the measurer, which invites bias; generalisation beyond the single client is a matter of replication rather than statistics; and withdrawal phases raise a real ethical problem when the intervention is working. Say which of these applies to the case you would use it on.

Likely learning objectives

Inferred from the brief — check these against your own rubric.

  • 01
    Present single-system design as a response to a specific inferential problem.
  • 02
    Distinguish AB, ABA, ABAB and multiple-baseline variants.
  • 03
    Define a target behaviour so it can be measured reliably.
  • 04
    State the design's limits, including bias and ethical withdrawal.
Assignment instructionsQuoted verbatim

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Discussion SOCW 6311 6070 Wk3 Discussions Discussion: SOCW 6311/6070 Wk3 Discussions Discussion1: Choosing and Using Single-System Design Many people receive their first introduction to the scientific method in their early school years. The first experiments which students undertake typically involve plants, chemicals, or small animals in a tightly controlled experimental environment. These experiments enable students to establish a relatively clear cause-and-effect relationship between the outcome of the experiment and the manipulation of the variables. As soon as a researcher introduces a human element, proving a cause and effect relationship becomes more difficult—as the researcher cannot enact total control of another person even in an experimental environment. Social workers serve clients in highly complex real-world environments. Clients often implement recommended interventions outside of social workers’ direct observation. Yet, evidence-based research calls for social workers to establish cause-and-effect relations between selected interventions and client outcomes as much possible. To meet this challenge, social workers must understand the study designs available to them and all of the variations of that design that can increase the rigor of the experiment and improve the likelihood of verifying a cause-and-effect relationship. In this week’s case study, you decide whether the social worker in the case study has appropriately chosen a single-system (subject) design and implemented it in such a way that it can be considered an appropriate example of evidence-based research. SOCW 6311/6070 Wk3 Discussions. To prepare for this Discussion, read the case study Social Work Research: Single Subject and criteria for using single-system (subject) designs as evidence of effective practices in this week’s resources. Consider whether the study design described in the case study will serve the purpose of evaluating the program’s practice approach (case management with solution-focused and task-centered approaches). Consider whether these approaches are well suited to evaluation by the types of measurement used in the study. Consider to what objective measurement the numerical scales used to measure problem-change and task completion corresponds. Consider what new knowledge and evidence for the efficacy of the treatment approaches Chris has generated with her study. · Post an evaluation of the proposed study design described in the case study file. · Explain whether the outcome of Chris’ study with her client George would lead you to adopt the model of case management with solution-focused and task-centered approaches, and substantiate your choice. · Provide recommendations for improvements should Chris and her colleagues wish to submit the study to the evidence-based practice registry. · Include a rationale for your recommendations. References (use 3 or more) Dudley, J. R. (2014). Social work evaluation: Enhancing what we do. (2nd ed.) Chicago, IL: Lyceum Books. · Chapter 9, “Is the Intervention Effective?” (pp. 226-244: Read from “Client Satisfaction & Effectiveness” to “Target Problem Scale”) Document: Corcoran, K., & Hozack, N. (2010). Locating assessment instruments. In B. Thyer (Ed.), The handbook of social work research methods (2nd ed., pp. 65–74). Thousand Oaks, CA: Sage. (PDF) Copyright 2010 by Sage Publications, Inc. Reprinted by permission of Sage Publications, Inc. via the Copyright Clearance Center. Document: Mattaini, M. A. (2010). Single-system studies. In B. Thyer (Ed.), The handbook of social work research methods (2nd ed., pp. 241–273). Thousand Oaks, CA: Sage. (PDF) Copyright 2010 by Sage Publications, Inc. Reprinted by permission of Sage Publications, Inc. via the Copyright Clearance Center. Plummer, S.-B., Makris, S., & Brocksen S. (Eds.). (2014b). Social work case studies: Concentration year. Baltimore, MD: Laureate International Universities Publishing. [Vital Source e-reader]. Read the following section: “Social Work Research: Single Subject” (pp. 70–72) Tankersley, M., Cook, B. G., & Cook, L. (2008). A preliminary examination to identify the presence of quality indicators in single-subject research. Education & Treatment of Children, 31(4), 523–548. Social Work Research: Single Subject Discussion SOCW 6311 6070 Wk3 Discussions Chris is a social worker in a geriatric case management program located in a midsize Northeastern town. She has an MSW and is part of a team of case managers that likes to continuously improve on its practice. The team is currently using an approach that integrates elements of geriatric case management with short-term treatment methods, particularly the solution-focused and task-centered models. As part of their ongoing practice, the team regularly conducts practice evaluations. It has participated in larger scale research projects in the past. SOCW 6311/6070 Wk3 Discussions. The agency is fairly small (three full-time and two part-time social work case managers) and is one of several providers in a region of approximately 50,000 inhabitants. Strengths of the agency include a strong professional network and good reputation in the local community as well as the team of experienced social workers. Staff turnover has been almost nonexistent for the past 3 years. The agency serves about 60–70 clients at any given time. The clients assisted by the case management program are older adults, ranging from their early 60s to over 100 years of age, as well as their caregivers. To evaluate its practice approach, the team has decided to use a multiple-baseline, single-subject design. Each of the full-time case managers will select one client new to the caseload to participate in the study. The research project is explained to clients by the respective case manager and informed consent to participate is requested. George was identified by Chris as a potential candidate for the evaluation. As a former science teacher who loved to do research himself, he agreed to participate in the project. George is 87 years old, and although he is not as physically robust as he once was, at 5 feet 9 inches tall, he has a strong presence. He has consistent back pain and occasional flare-ups of rheumatoid arthritis. His wife of 45 years passed away two summers ago after a long fight with cancer. After his initial grief, he has managed fairly well to adapt to life on his own. George entered the program after being hospitalized for fainting while at the grocery store. A battery of medical tests was conducted, but no specific cause of his fainting attack could be found. However, the physicians assessed signs of slight cognitive impairments/dementia and suggested a geriatric case management program. An initial assessment by the case manager showed the need for assistance in the following areas: 1) personal care, 2) decrease in mobility, and 3) longer-term planning around living arrangement and home safety. The case manager also thought that George could benefit from setting up advance directives, which he did not want to discuss at that time. They agreed that the case manager could bring this topic up again in the future. SOCW 6311/6070 Wk3 Discussions. As part of the practice process, the case manager used clinical rating scales that were adapted from the task-centered model. At the beginning of each client contact, case manager and client collaboratively evaluated how well the practice steps (tasks) undertaken by client and/or case manager were completed using a 10-point clinical scale. Concurrently, they evaluated changes to the respective client problems, also using a 10-point clinical scale. George was able to actively participate in the planning and implementation of most care-related decisions. During the course of their collaborative work, most needs were at least partially addressed. Two tasks were completed regarding personal care, two regarding mobility, and three addressing home safety issues. Only personal mobility was still a minor problem and required some additional work. After finishing the reassessment at 3 months, Chris completed gathering and evaluating the data for the single-subject design (SSD). As promised, she also provided George with the finished SSD findings. The following is an overview of the data that was collected for this case: Plummer, Sara-Beth, Sara Makris, Sally Brocksen. Social Work Case Studies: Concentration Year. Laureate Publishing, 10/21/13. VitalBook file.
02

Turn the brief into deliverables

  1. 01
    The inferential problem the design responds to.
  2. 02
    The logic of using the client as their own control.
  3. 03
    The design variants and when each applies.
  4. 04
    An operationally defined target behaviour.
  5. 05
    Baseline requirements and what a rising baseline means.
  6. 06
    The design's limitations, applied to a real case.
03

Why cause and effect is hard, then how the design handles it

01

Why the human element makes inference hard

State the problem the design is responding to.

02

The client as their own control

Explain the logic of repeated measurement across phases.

03

The variants

Distinguish AB, ABA, ABAB and multiple baseline.

04

Defining the target

Operationalise a behaviour so it can be counted.

05

Baseline

Explain how long, and what a trending baseline implies.

06

Limits and ethics

State what the design cannot establish and where withdrawal is wrong.

04

Single-system design sources and their limits

Recommended databases

  • PubMed Central
  • Campbell Collaboration
  • The assigned course readings
  • Social work research texts

Search sequence

  1. 1.
    Take the design notation from the course text so it matches the marking.
  2. 2.
    Search for published single-system studies in social work rather than in behaviour analysis alone.
  3. 3.
    Look up visual analysis conventions for reading phase change.
  4. 4.
    Find one critique of the design's causal claims.
05

Reference shortlist

These are authoritative starting points, not a ready-made bibliography. A qualified reviewer must confirm that each source fits the assignment and supports the claim beside which it is cited.

Nothing here is cleared for citation until you have read it.

  1. 01

    Quantitative Methods

    University of Southern California Libraries · 2025

    Design and measurement fundamentals, including threats to internal validity.

  2. 02

    Logic analysis: testing program theory to better evaluate complex interventions

    Canadian Journal of Program Evaluation · 2011

    Testing programme theory — the logic behind attributing change to an intervention.

  3. 03

    Qualitative Study

    StatPearls, NCBI Bookshelf · 2023

    Qualitative approaches, as the alternative when counting is not the right instrument.

  4. 04

    Exploratory Data Analysis: Frequencies, Descriptive Statistics, Histograms, and Boxplots

    StatPearls, NCBI Bookshelf · 2023

    Descriptive analysis and visual inspection of data over time.

  5. 05

    Theories Used in Social Work Practice & Practice Models

    Simmons University, School of Social Work · 2024

    Where practice evaluation sits among social work's methods.

06

Review before submission

Common mistakes

  • Describing the design without connecting it to the causal problem the prompt raises.
  • Choosing a target that cannot be counted reliably.
  • Ignoring baseline trend, which undermines any later attribution.
  • Proposing a withdrawal phase for an intervention that is helping.

Submission checklist

  • Is the design presented as an answer to the prompt's problem?
  • Could two observers count your target the same way?
  • Have you addressed baseline length and trend?
  • Are the limitations applied to a specific case rather than listed?

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