Blog 1 – The difference between a case study and single case designs

My aim of this blog is to explain to you the difference between a case study and single case designs. I am hoping to do this without the use of text book jargon as there is nothing worse than having to constantly refer to a thesaurus or Wikipedia when trying to read and comment on blogs. Here goes….

A case study is a research design that involves in depth description of a single individual or sometimes one very small group.Case studies are often used to provide information about rare and unusual behaviours, also to demonstrate exceptions to the rules.
An advantage of case studies is that they can bring to attention any new variables that might account for a particular outcome. Case studies however are often weak in external and internal validity as the theory and observations can only be generalised to that particular individual/case.
A very rare example of a case study was the girl Oxana Malaya who is now 28. She was found at the age of 8, in the Ukraine, living as a feral child. Having spent most of her life raised by dogs, she picked up many of their habits and norms. This was an extraordinary case that gave psychologists the opportunity to explore development and social issues. To learn more, you can check out this youtube video…

 A single case design is also known as a single subject design. It is a research design that, like many others, aims to establish a cause and effect relationship. A single case design, however, uses the results from a single participant to do this. A series of observations are made over the participant. These are called the baseline phase and the treatment phase. The baseline phase is the stage at which observations are made in the absence of a treatment and the treatment phase is the stage at which observations are made during the treatment. The collection of these observations should show a pattern that describes the behaviour and the important part is the consistency or stability of this pattern. A researcher may change phases by applying or withdrawing a treatment and this is done to show that by adding or removing a treatment, there is an obvious change in behaviour. The researcher interprets the results not using SPSS or traditional tests, they must use graphs to interpret the results. This means that the graph must show a change in the behaviour more than once so it is clear that the first change was not due to chance.

You may be thinking that this is a very subjective method to interpret the results…it is. There are, therefore, four specific characteristics to help researchers determine whether changes are meaningful.

  1. Does the graph show change in the average level of behaviour?
  2. Does the graph show immediate change in level of behaviour?
  3. Does the graph show change in trend of behaviour?
  4. Does the graph show latency of change in behaviour?

The primary advantage of using a single case design is that they can use flexible methods to allow cause and effect relationships to be shown with one participant. The main disadvantage is that the results can only be generalised to this one individual.


Viewing both separately, it is easy to distinguish the differences. The main being that with single case designs, the researcher is in full control of what is going on in the experiment and they can manipulate it to whatever extent needed. In case studies, however, it is common that psychologists are not able to explore results until after changes have occurred. The cannot manipulate the process/development of the case.

 I’m sorry this blog may seem a little rushed, it’s because I’m getting the train in an hour to go home for my 21st 😀



3 thoughts on “Blog 1 – The difference between a case study and single case designs

  1. psucd8 says:

    I think you have summarised the differences between case studies and single-subject designs really well. It is important to realise that case studies are often used for forming hypotheses whereas a single-subject design is experimental (or quasi-experimental in some cases) therefore is testing hypotheses. You have mentioned that a disadvantage of this kind of design is that the results can only be generalised to one individual, however this could be seen as an advantage as well. Psychology is a field which acknowledges that every individual is different, therefore one form of intervention will be more effective on some individuals than others.
    A version of a single-subjects design that is sometime used in the clinical field is the n of 1 trial, where the effectiveness of a therapy (whether drug or not) is analysed for a single individual. Researchers have found that the success of treatments is much higher for individuals who have been part of this research than of those who have been treated based on group research methods, see Kravitz et al. (2008), p. 542. Therefore, in a field where it is the individual differences and the effectiveness of treatments on individuals to improve their lifestyles that is important, then a research method which focuses on each individual to ensure they receive the appropriate care required rather than generalising from many participants could be seen as a major advantage of the design, see Lillie et al. (2011).

    Kravitz et al:
    Lillie et al:

  2. katepsuc7d says:

    I thought this blog was explained well and I enjoyed reading it, because it was clear to understand.

    I agree there are major differences between the case studies and single case design, but it is very important to be have different forms of methodology because we couldn’t research everything with one research design. I think case studies are very important because they are very specific, I think the unique cases are interesting and even if they are not common they still show amazing things about human behaviour, and I think it is worth knowing about. But there has also been a lot learned from single case designs and there is a usually a wider variety of things that can be tested using quantitative methods. I think both of these methods are important to psychology and should be used where possible, because we study behaviour I believe generalisble behaviour and unique behaviour is equally important.

    I enjoyed your choice of video too, I remember learning a similar case when studying feral children in college and it is quite fascinating.

    I hope you enjoy your birthday 🙂

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