The types of research you will encounter when searching for evidence-based practice information resources will include qualitative and quantitative research. Keep in mind that research studies do not have to be exclusively one or the other, many studies will use a combination of both these types of research.

While the levels of evidence you will encounter when searching for evidence-based practice information will include secondary evidence and primary evidence.

Quantitative research is used to generate numerical data or data that can be converted into numbers. Study types that are used in the health and medical field include:  

• Case report or case series - a report on one or more individual patients.  There is no "control group" so this study type is considered to have low statistical validity
• Case control study - this studies patients with a particular outcome (cases) and control patients without the outcome. Is useful in aetiology (causation) research but prone to causation error
• Cohort study – identifies and follows two groups (cohorts) of patients, one having received the intervention being studied, and and one having not. Useful in both aetiology and prognosis research. Because the groups are not randomised, they may differ in ways other than in the variable under study
• Randomised Controlled Trial (RCT) - a clinical trial in which participants are randomly allocated to a test treatment and a control. This is considered the “gold standard” in testing the efficacy of an intervention. RCTs include methodologies - randomisation and blinding - that reduce the potential for bias and provide good evidence for cause and effect.

Qualitative research is used to explore and understand people's beliefs, experiences, attitudes, behaviour and interactions. It generates descriptive, non-numerical data.  Qualitative research methods include:

• Documents - the study of documentary accounts of events, such as minutes of meetings
• Passive observation - the systematic watching and recording of behaviour  
• Participant observation – here, the researcher also occupies a role or part in the setting, in addition to observing
• In-depth interview - a face-to-face conversation to explore issues or topics in detail
• Focus group - method of group interview which explicitly includes and uses the group interaction to generate data.

There are two broad types of evidence: secondary and primary. Note that we list secondary first because in Evidence-Based Practice it is the higher level of evidence and will probably be what you seek first in answering a clinical or research question.

• Secondary evidence (filtered, pre-appraised)

Evidence that is assimilated, or put together, from a number of quality primary studies on a topic. It includes systematic reviews, meta-analyses, and evidence summaries. This is sometimes referred to as filtered or pre-appraised evidence. You can find it in specialised EBP sources such as The Cochrane Library (notably in the Cochrane Database of Systematic Reviews) and JBI COnNECT+ on Ovid (see Accessing JBI Tools for the first time), and in health and medical databases such MEDLINE, PubMed and CINAHL Plus with Full Text.

• Primary Evidence (unfiltered)

This body of evidence consists of original individual studies such as controlled trials, cohort studies, and case studies. This is sometimes referred to as unfiltered evidence. You can find primary studies in specialised EBP resources such as The Cochrane Library, notably in the Central Register of Controlled Trials, and in health and medical databases. You can search for primary research in journal databases such as CINAHL Plus with Full Text and Medline.