Once you have searched for information, you will need to critically appraise the studies you have found. This is a really important process because it ensures that studies with scientific flaws are disregarded, and the ones you include are relevant to your research question.

When evaluating primary research (research which hasn't been pre-appraised or filtered by others), you need to make sure the evidence you are including in your review is scientifically rigorous. The main questions to address are:

• Is the study relevant to your question?
• How scientifically did the researchers design the study, especially in their care to eliminate bias?
• What do the results mean and are they statistically valid (not just due to chance)?

For a more detailed look at Critical Appraisal, head to the Systematic Review Guide - Critical Appraisal and the Evidence-Based Practic Guide - Appraise.

Peer-reviewed articles are:

• written by subject experts
• reviewed by other subject experts ("peers')
• published in peer-reviewed journals.

Peer-reviewed journals are sometimes called refereed journals.

Peer-reviewed articles and journals are regarded as being more scholarly and authoritative than article and journals that are not peer-reviewed.

Watch this video for an explanation of peer review and how to check that a journal is peer-reviewed. For written explanations, see: How to check if a journal is peer-reviewed.

Original or Primary Research 

These articles are reports of original research and typically include a hypothesis, a short literature review, methods, results, an interpretation of findings, and a discussion of possible implications. 

Review Articles

Review articles provide a summary and an evaluation of research on a topic. The review will also identify gaps in knowledge, which will help identify further research that needs to be done. There are many types of review articles- narrative, scoping and systematic reviews being common.

Case Studies

A case study is a report of an instance involving an in-depth, detailed examination of an organisation, event, action, or person over a defined period of time.

Clinical Trials

Clinical trials articles report the results of investigations in which people have volunteered to test new treatments, interventions or tests for managing various diseases or medical conditions. 

Methodologies or Methods

These articles present an experimental method, test or procedure. 

Perspective, opinion, and commentary

These articles express an expert's personal opinion or experience, or a new perspective about existing research on a particular topic.