Critical appraisal of quantitative and qualitative research literature

Critical appraisal of research articles can be used to inform the design of new research studies. It can also be used by clinicians who wish to improve service quality by using the best available evidence to inform their practice. This paper describes a broad framework of critical appraisal of published research literature that covers both quantitative and qualitative methodologies. The aim is the heart of a research study. It should be robust, concisely stated and specify a study factor, outcome factor(s) and reference population. Quantitative study designs, including sampling methods, can be ranked in order of the quality of the evidence they produce, with randomised control trials being ranked as level 1. The strength of evidence from qualitative research studies depends on the degree of rigour used in data collection and analysis, using techniques like theoretical sampling, triangulation and participant validation. Whatever the study design, it must be appropriate to address the aim of the study. In critically appraising all research papers, there is a need to reflect on how well the conclusions flow logically from the results of the analysis and answer the original research question and how well the research applies to the population we are interested in. Short communication the other hand, refers to the “consistency” or “repeatability” of a study – Is the study reproducible? Well designed research, with good reliability, could be repeated at a different time or using a different population and give comparable results. Like validity, reliability has a number of types, the best known being inter-rater or inter-observer reliability. All research is not of equal quality in terms of validity and reliability. When reading a research paper we are justified in reading critically and questioning the findings, especially whether or not we should accept the conclusions drawn from the study and adopt the recommendations. However, being critical is a challenge for both clinicians and early career researchers, generally because they assume that the researchers must be more expert than themselves. There is a tendency to believe that any research study that has made it into print must be of the highest quality. This is not universally true. Editors and publishers choose papers for a variety of reasons. Furthermore, journals also vary in terms of the quality of the papers they publish and they are rated according to an impact factor. However, even journals with a high impact factor publish research of dubious quality, again, for various reasons. The first step in critically appraising a research article, therefore, is to reflect on the quality of the journal in which it is published. The second is to examine the track record of the authors in the particular field of study – Where are they from? What are their qualifications? Have they published in this field before? A search of Google Scholar or the Medline database can quickly answer these questions. Some excellent resources are available to help develop critical appraisal skills. Concise, logically structured, analytical approaches are described by Darzins, et al. and by Greenhalgh. The latter wrote a series of papers on research methods in the British Medical Journal – a valuable resource! The critical appraisal framework described below synthesises the work of these and other authors. The Radiographer 2009; 56 (3): 6–10 Australian Institute of Radiography