Question

What are your pre-conceptions about single-case research designs? Does conducting research evaluating the behavior of a single individual provide useful information, or must we use large-group designs to get real data regarding behavioral phenomena? What are the advantages and disadvantages of a single-case design as compared to a group design?

Answer 1

Single case research design or single subject research or single case experiment design is a study in which the researcher studies the behavior of an individual or a small group of individuals. This type of study is employed when the researcher is interested in attempting to change the behavior of the individual and wants to record the changes. In single case experimental design, the individual is not randomly assigned to the treatment group and the control group. The individual serves in both the groups and only one variable is changed at a period of time. This type of research is used in intervention / counselling in order to study the effect of the treatment and to document the change in behavior. In order to measure the change in behavior, the subject is first measured on the variable that is of interest in the study. The behavior is measured 3 times in order to identify a pattern which will serve as the baseline measure. The intervention will be administered and the subject will be tested again after a period of time in order to measure whether there was a change in behavior. The results of the study are presented through line graphs in order to see the changes occurred. This design solely relies on visual presentation as statistical analysis cannot be performed.

Another form of single case research design is Reversal design. This constitutes of 4 phases namely; baseline, treatment, return to baseline and second treatment phase. The goal here is to assess whether the changed behavior after treatment can be reversed to the baseline behavior. This is done to determine whether the treatment indeed caused the change in behavior

Single case design is extremely useful as it provides detailed information about a change in behavior. The researcher can focus on one participant and observe the change in behavior. However, in order for an intervention to be generalized, it has to be replicated numerous times and have to show consistent results. Thus results of a single case study cannot be generalized as it has low external validity (ability of a test to be applicable across different settings and individuals).

Advantages:

• Single case design is an extremely powerful design as the researcher is able to receive feedback immediately and is able to make changes accordingly. If the treatment is not working, the researcher can make the necessary changes. Whereas, the results from a large group design will take a longer period of time because multiple participants are involves and statistical tests have to be used. The results can only be interpreted at the end of statistical analysis
• The cause and effect of the treatment through change in behavior can be determined through a single case study

Disadvantages

• There is no random assignment of participant to control group and treatment group. The results from a single study cannot be generalized and hence external validity is low. Since the results are not replicated, the reliability is also questioned
• Multiple observations on the individual can affect the individual’s response
• Single it’s a single case study, there will not be any statistical analysis
• In the reversal design, in some cases the treatment cannot be assessed as there can be long lasting effects
• The ethics can be questioned in the reversal design as successful treatment is withdrawn from the participant