Research in Practice for Forensic Professionals by Kerry Sheldon Jason Davies Kevin Howells

Author:Kerry Sheldon, Jason Davies, Kevin Howells [Kerry Sheldon, Jason Davies, Kevin Howells]
Language: eng
Format: epub
Tags: Nonfiction, Social & Cultural Studies, Social Science, Crimes & Criminals, Criminology
ISBN: 9781136647284
Publisher: Taylor and Francis
Published: 2012-03-12T04:00:00+00:00

Basic principles of single case designs

Many designs are used within the single case framework; however, all follow the same logic – that is measurement covering more than one phase. In the most basic form of this approach the two phases are known as baseline (the period before the treatment is introduced) which is denoted by an A, and intervention which is denoted by a B. Sometimes this design will also incorporate a period of follow-up during which the ‘lasting effects’ of the intervention can be tested. This is simply referred to as A, B with follow-up. The case study later in the chapter (and Figure 8.4) show such a design. There are many examples of this design in the literature such as Smith, Handler and Nash (2010) who used this design to investigate the impact of therapeutic assessment with three boys with oppositional defiant disorder and their families. In this study the authors identified five or six variables in conjunction with each family to be recorded on a daily basis. These were specific to each individual child. Recordings were made for at least 10 days prior to treatment (baseline); during the nine weeks of treatment and at a follow-up point which occurred at least 60 days after the intervention ceased. Unlike classical experimental/control group designs in which the comparison is between groups, single system designs involve a comparison between time periods for the same individual. The underlying assumption is that if the intervention had not occurred, the pattern of events occurring during the baseline is likely to have continued to occur as before.

Although most psychological interventions are not reversible (i.e. they cannot be completely removed or undone), where interventions can be taken away with the expectation that the individual would return to their pre-intervention state without them (as in the case of the withdrawal of many medications or with some environmental or contingency management programmes) the design would be described as an ABA design. An example of such a design is presented by Freeman et al. (2010) who used this design to test the impact of an exercise programme on balance and mobility in individuals with multiple sclerosis. In their study the same measures were made weekly over a four-week baseline period, eight weeks of intervention and four weeks of withdrawal. An important consideration in ABA designs is the ‘absolute’ extent to which the withdrawal or reversal is achieved. For example in the Freeman et al. study, careful checking would be necessary to ensure that all individuals followed the instruction to cease home exercise (especially if they believed it had made a difference to their functioning). Where more than one intervention is studied, different interventions are given different letters (C, D and so on). An example of this would be a baseline (A) followed by the introduction of mindfulness (B), followed by a cognitive intervention (C) and finally a family intervention (D).

Regardless of the design, data should be collected for a period of time long enough to be useful for the assessment and evaluation of progress (Bloom et al.

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