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Source Types

Sources are considered primary, secondary, or tertiary depending on the originality of the information presented and their proximity or how close they are to the source of information. This distinction can differ between subjects and disciplines.

In the sciences, research findings may be communicated informally between researchers through email, presented at conferences (primary source), and then, possibly, published as a journal article or technical report (primary source). Once published, the information may be commented on by other researchers (secondary sources), and/or professionally indexed in a database (secondary sources). Later the information may be summarized into an encyclopedic or reference book format (tertiary sources).

Primary Sources

The first place researchers publish their research findings. A primary source in science is a document or record that reports on a study, experiment, trial or research project. Primary sources are usually written by the person(s) who did the research, conducted the study, or ran the experiment, and include hypothesis, methodology, and results. Typically in the form of journal or research articles that follow a typical research article structure. The hierarchy of evidence (the evidence pyramid) is based on the type of study and and quality of evidence. Examples: Randomized Controlled Trials, Cohort Studies, Case-Control Studies, Case Reports, Qualitative Studies

Primary Sources include:

  • Pilot/prospective studies
  • Cohort studies
  • Survey research
  • Case studies
  • Lab notebooks
  • Clinical trials and randomized clinical trials/RCTs
  • Dissertations

Secondary Sources

Often this may involve a clinician reviewing research to answer a clinical question. Examples: Systematic Reviews, Meta-Analyses, Evidence-Based Guidelines, Some Clinical Database entries

Secondary sources list, summarize, compare, and evaluate primary information and research in order to collate and evaluate research, draw conclusions, present current states of knowledge in a discipline or subject. Sources may include a bibliography which may direct you back to the primary research reported in the article, systematic reviews, meta-analysis, evidence-based guidelines, and some clinical database entries.

Secondary Sources include:

  • reviews, systematic reviews, meta-analysis
  • newsletters and professional news sources
  • practice guidelines & standards
  • clinical care notes
  • patient education Information
  • government & legal Information
  • monographs
  • entries in nursing or medical encyclopedias

Tertiary Sources - Health information sources that collate research literature from multiple sources. Evidence may be lacking currency compared to primary sources. Examples: Most guidelines and society statements, Most Clinical Database entries, Clinical Textbooks, Narrative Reviews

Good overview of primary & secondary sources from UViC Library


More on Systematic Reviews and Meta-Analysis

Systematic reviews – Systematic reviews are best for answering single questions (eg, the effectiveness of tight glucose control on microvascular complications of diabetes). They are more scientifically structured than traditional reviews, being explicit about how the authors attempted to find all relevant articles, judge the scientific quality of each study, and weigh evidence from multiple studies with conflicting results. These reviews pay particular attention to including all strong research, whether or not it has been published, to avoid publication bias (positive studies are preferentially published).

Meta-analysis -- Meta-analysis, which is commonly included in systematic reviews, is a statistical method that quantitatively combines the results from different studies. It can be used to provide an overall estimate of the net benefit or harm of an intervention, even when these effects may not have been apparent in the individual studies [9]. Meta-analysis can also provide an overall quantitative estimate of other parameters such as diagnostic accuracy, incidence, or prevalence.

Qualitative vs. Quantitative Research

These are different research methods to acquire answers to social phenomena. You can differentiate between qualitative and quantitative research by looking at the outcomes and goals of the research and processes involved. 

Qualitative Research: Research that involves sensory research methods such as interviewing, listening or observing to gather and organize data into patterns or themes, observations (Maricopa College, n.d.). Examples include case studies, phenomenological studies, grounded theory, and ethnographies (Smith, 2017). More information on qualitative research. Qualitative research an be difficult to reproduce, such as observational studies. 

Quantitative Research: Research that intends to identify a relationship between one thing (an independent variable) and another (a dependent or outcome variable) in a given population. The two types of quantitative research methods are experiment or survey/descriptive. A descriptive research study usually establishes associations between variables. An experiment usually establishes causality. Methods usually involve measuring subjects and reporting results. Usually the study or article will outline how subjects were selected, how many subjects participated, and how a random sample was selected (Smith, 2017) . More information on quantitative research.

Mixed methods studies use both research approaches, producing both qualitative and quantitative data that can be used to provide insight and answer research questions.

McGill University provides an excellent comparison table, as well as a number of examples.Or see this chart for the differences between the two types of research.

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