Hierarchies of evidence help you to identify the most robust evidence to answer your research question by helping you decide what evidence to look for. Generally study designs towards the top of the hierarchy have measures in place to minimise bias, so they are good places to start.
Different research questions require different study designs, so there is no one hierarchy of evidence. The pyramid below details a hierarchy of evidence for effectiveness questions, i.e. are steroid tablets more effective than combination inhalers in treating adults with severe asthma?
There won't always be high level evidence such as systematic reviews or randomised controlled trials available in the area you wish to research, so you will need to consider evidence further down the pyramid.
University of Exeter LibGuide is licensed under CC BY 4.0
