SINGLE-SUBJECT DESIGNS

SINGLE-SUBJECT DESIGNS

1. 1. INTRODUCTION

   • Offer an alternative to GROUPS DESIGNS
   • Focus is on an N=1, a single subject - "1" can be an individual, an agency, or a community
   • USeful fro research on interventions in direct and community practice - The process of assessment, establishing intervention goals and specific outcomes, and evaluating progress have direct parallels to the structure of single-subject designs, which depend on identifying target problems, taking pre-intervention measures, providing the intervention, taking additional measures, and making decisions about the efficacy of the intervention
   • Useful in evaluating practice and improving client outcomes through monitoring a client's progress

2. 2. FOUNDATIONS OF SINGLE-SUBJECT DESIGN

   • Underlying principle-should be possible to see a change in status from the period prior to intervention/modification of behaviour to period during and after the intervention
   • Minimally has 3 components: a) REPEATED MEASUREMENT, b) BASELINE PHASE, c) TREATMENT PHASE
   • a) Repeated measurement: - The same behaviour is measured over and over again - different from most experiments, in which the dependent variable is measured only one - needed to obtain clear pattern or consistency in the behaviour over time - Control for the normal variation of behaviour that is expected within short time intervals
   • b) Baseline phase: - refers to a period of time in which the target behaviour is observed and recorded as it occurs without a special or new intervention - provides the frame of reference against which future behaviour is compared - Can also refer to a period of time following a treatment in which doncitiones match what was present in the original baseline
   • c) Treatment phase: - A period of time during which the experimental manipulation is introduced and the target behaviour continues to be observed and recorded

3. 3. TYPES OF SING-SUBJECT DESIGNS

   • 1. A-B-A Withdrawal Designs; 2. Multiple Baseline Designs, 3. Multiple Treatments Design

4. 4. A-B-A WITHDRAWAL DESIGNS

   • A refers to the non-treatment or control phase of the experiment, B refers to the treatment phase of the experiment
   • i) A-B DESIGN
     • Simplest variant of A-B-A withdrawal designs - Includes a baseline phase with repeated measurements and an intervention phase continuing the same measures
     • E.g. Two parents having problems with one of their children - over past month, their 16-year-old daughter has been squabbling constantly with her brother and being rude and sarcastic with her parents - Suggest that the parents use POINT SYSTEM, with points being given for poor behaviour - Once a number of points are attained the child begins to lose certain privilges
       • Parents are instructed to count and record every 3 days over a 15-day period the number of instances of sibling arguments begun by the child and the number of rude and sarcastic comments - The intervention begins on the 16th day, with the parents explaining how the child might get negative points and face the consequences of accumulating points
     • LIMITS: - design cannot rule out history and impossible to conclude that the treatment is caused by change (e.g. improvement may have been due to child stopping relationships at the start of the intervention with peers who were teasing her)
   • ii) WITHDRAWAL DESIGNS: A-B-A & A-B-A-B
     • Two withdrawal designs: - intervention is concluded (A-B-A) or is stopped for some period of time before it is begun again (A-B-A-B) - If the intervention is effective, the target problem should be improved only during the course of intervention, and the target scores shouldworsen when the intervention is removed - If this assumption is correct, the impact of history between the baseline and intervention phase would not explain the change
     • i) A-B-A Design:- Builds on the A-B design by integrating a post-treatment follow-up that would typically include REPEATED MEASURES - the design answers the question left unanswered by the A-B design - whether the effect of the intervention persist beyond the period in which treatment is provided
     • ii) A-B-A-B Design:- Builds in a second intervention phase - The intervention in this phase is IDENTICAL to the intervention used in the first B phase
     • LIMITS:- The withdrawal designs suffer from the problem that often the target behaviour cannot be reversed, and it may not be ethical to withdraw treatment early

5. 5. MULTIPLE BASELINE DESIGNS

   • Solution to ethical issues in withdrawal design is to add ADDITIONAL SUBJECTS, TARGET PROBLEMS, OR SETTINGS to the study
   • The basic format is a CONCURRENT MULTIPLE BASELINE DESIGN, in which a series of A-B designs are implemented AT THE SAME TIME for at least 3 CASES (CLIENT, TARGET PROBLEMS, OR SETTINGS) - Therefore, data are collected at the same time
   • The unique feature of this design is the LENGTH OF THE BASELINE PHASE is STAGGERED to control for external events (i.e. history) across the three cases
   • Multiple baseline designs are useful - introduce two replications so that if conssitent results are found, the likelihood that some external event is causing the change is reduced

6. 6. MULTIPLE TREATMENT DESIGNS

   • Nature of the intervention changes over time, and each change represents a new phase - One type of change = intensity of intervention (e.g. You might work with a family with communication problems - The actual amount of contact you have with the family may change over time, starting with counselling sessions twice a week, followed by weekly sessions, and concluding with monthly interactions - Amount of contact declines over time
     • A-B1-B2-B3
   • Another tyoe - you add additional tasks to be accomplished (E.g. older adults who lose their vision need to relearn how to do different independent activities of daily living - Intervention is learning independent self-care - B1 = walking safely within the house; B2 = add methods for using a check-book; B3 = adds a component of cooking
   • The actual intervention may change over time and therefore the multiple treatment designs phase reflects these changes - A-B-C-D - with B, C, D phases representing different interventions

7. 7. POSITIVES & NEGATIVES

   • Single-subject designs offer a range of evidence to assess the impact of different interventions/modifications
   • BENEFIT: The focus on the individual as opposed to a group - evidence derived differs from that of group designs in that they question whether the intervention works for an individual
   • NEGATIVE: The strength of the design is also it's weakness - Questions around how findings about a single individual should be judged and how evidence is relevant to other clients - problems about building generalisability of the findings