The first step in critical appraisal – deciding what design your research study uses.

Critical appraisal has been made much easier by the development of tools that guide you through the process of what aspects of the research study you should be evaluating.  Some argue that it isn’t until you become experienced in research methods that you can properly evaluate the quality of the methods used by others.  I think this is a valid point but we all have to start somewhere, and critical appraisal is one of the best ways I know to learn about research methods if you aren’t able to actively do a research project.

The quality of a research study is determined by how appropriate the approach, the design and the methods used were to address the question.  The first decision we make when evaluating a study therefore is whether this question would be best answered using a qualitative approach (using interviews or focus groups to find out about people’s experiences) or a quantitative approach (collecting data using questionnaires and measurement tools).  Some questions are best answered by using a combination of both approaches (mixed methods or multi-methods).  Quite often the person undertaking the critical review will decide ahead of time (a priori) which approach is appropriate and use that as an inclusion criterion for the retrieval of papers.

Once you can determine the approach a study has taken you move onto deciding what design the researchers have used.  As a novice this can be particularly difficult.  If you are lucky the researchers have included the design in the abstract of their paper. If not, you will have to work it out by looking at whether there is a hypothesis or not (usually a sign of a quantitative analytical study) or an aim (usually a sign of an observational study).

Here are some notes about different types of studies, with thanks to Josette Bettany-Saltikov from whose book ‘How to do a systematic literature review in nursing‘ I have adapted the diagrams.

Quantitative designs

Case reports and case series

A report of the treatment of a single patient or more than one patient. Usually published because the condition or treatment is very rare.

Case report

Case control studies

Patients who have a condition are compared with those who don’t.  The data for the study is taken from the medical records and patient recall (memory).

Case control studies

Cohort studies

This design follows a large group of people for a long time who all have the condition of interest, usually as they receive a treatment, or to observe how the condition changes.

Cohort studies

Randomised controlled trials

Used to explore the effect of treatments by comparing a group who are given the treatment with one who are not.  The strength of the design is that by randomly allocating patients to the active and control groups you will end up with broadly similar people in each group (in terms of the variables that could inadvertently influence the outcome being measured).


Qualitative designs


Exploring the lived experience of a group of patients or staff.


Describing a culture – usually by becoming part of that group to understand it.  Good to understand how people see their own experiences.

Grounded theory

The researcher aims to develop a theory that explains events and behaviours.

The other aspect to design is to determine when the data was collected and whether it was taken from a source that already existed (e.g. the patients’ notes) or whether it was collected for the study.

  • At one point in time = cross-sectional
  • At several time points = longitudinal
  • Data that already existed and was collected for a different purpose = retrospective
  • Data is being collected for the research study = prospective.

Once you have a basic idea of what types of study there can be you can usually work out what the design is even if the authors don’t state it.

You might find this decision tree for research design helpful.  Feedback would be very helpful to improve the design of this resource.

Research design flow diagram

I’ve found a published review like the one I want to do…help!

It is quite common that you come up with a research question for your dissertation review, or for a review you wanted to publish and then you find a systematic review on the same subject has already been published- can you still go ahead anyway?  There is a simple answer and a more complicated answer.  If you don’t mind thinking of a brand new question the simple answer is no, don’t go ahead.  However, the reason you are asking what you can do about the situation suggests that you want to hold onto your question despite finding this other review.  That makes the situation a little more complicated.

First I’ll describe what a review is, and then I will discuss why repeating a review is inappropriate, and then what you can do if you just can’t let go of your idea.

A review is form of research.  It allows you to bring together information from a variety of sources and synthesise it.  A synthesis is when you combine component parts to create a whole.  Usually the whole is greater than the sum of the parts. In a review you find as much information as you can that will help you generate an answer to your research question.  Often you are asked to restrict the information type to peer reviewed primary research studies – studies in which data has been collected.  You decide during the critical appraisal phase whether the primary research is trustworthy, and it is you include it in your synthesis.

A review is conducted when the research question can be answered by combining (synthesising) the results of already published primary research.  Its no good trying to answer a question by review if there is very little or no primary research.  If there is very little primary research then you would need to do primary research.  If someone has already answered your research question by undertaking a review then you won’t find anything different to them – so it is pointless repeating what has already been done.  However, of course there are exceptions to this rule and that is how we arrive at the third part of this blog -reasons to go ahead anyway.

  • A review has been conducted a relatively short while ago but since then there have been a number of new primary research papers published – then you should go ahead and update the previous review.
  • The review was poor quality or didn’t include all the relevant primary research – then you can go ahead and do a better job.
  • The review was broad in scope – then you can identify a similar question that enables you to take a new perspective on the topic.

Creating a question for your dissertation.

I’ve just launched our Undergraduate dissertation for the nursing students.  These third years will, over the next 6 months, develop a research question and answer it using a critical systematised review method.  The task seems to create a great deal of anxiety and we try to manage that by using a check-list approach.

The very first task is coming up with a research question.  For those of us in working in academe and the NHS this seems like a fairly easy task – we are often brimming over with questions we want to know the answer to.  However, many UG students find this task really difficult.  So how do you come up with a research question when you feel like your head has suddenly emptied of all thought?

Well, you have to start by trusting yourself.  Anxiety seems to be the enemy of creativity.  Get a sheet of paper and just write down what you are interested in.  It doesn’t matter what words you use – don’t worry about the right vocabulary just write.  There is a free writing technique that can be used to overcome a real block.  In free writing you just write down what you see in front of you, and then carry on writing anything that comes to mind.  This can be helpful to get over the fear of the blank page.  It doesn’t matter that most of what you have written will have to go in the bin – it got you started and so it is useful.

Now, you should have some words and these words will hopefully trigger you to write other words and gradually you will see emerge something that interests you.  Grab the thing that interests you and pursue it.  Write down why it interests you.  If you can’t grab hold of the thoughts then start talking.  Talk to yourself, your cat, a person, and tell them about your idea.  If you have to start with just saying a word then do that.  If you have chosen to discuss your idea with a human they can help you to explore it by asking you questions.  Jot down some notes.  At the end of the process you will have an idea of what your question might look like.  It doesn’t matter at this stage it is fully formed or not – it is a question of sorts – you have succeeded.

The next stage is to refine the question and that will be dealt with in another blog.