3 Evaluating Sources and Reviewing Literature
Learn how to evaluate sources in relation to a research question, synthesize studies into a literature review, and identify research gaps responsibly.
Evaluating sources in context
Evaluate a source in relation to the question you are investigating, rather than relying on a single clue such as a professional-looking website or a “peer reviewed” label. is contextual: the expertise or experience that makes a source useful depends on the question.
Applying the four evaluation questions
Use four connected questions to judge how a source can contribute to your research:
: Are the claims supported by checkable evidence? Does the source distinguish evidence from opinion, explain its methods, and cite relevant sources? For a research study, consider whether its methods and data support its conclusions.
: Does it address your specific question, population, place, and time period? Reliability alone does not mean a source answers your question.
: Who created or published it, and what qualifies them to speak on this topic? Consider relevant expertise, professional or community experience, the publisher’s standards, and the source’s role in its field. Lived experience may be important evidence for some questions, but does not automatically establish expertise on every related claim.
: Who produced it, for whom, and to what end? Consider advocacy, commercial interests, political commitments, selective evidence, and assumptions that shape what is included. Bias does not automatically make a source useless; identify its effect on the claims and weigh the source alongside other evidence.
For online sources, investigate beyond the page itself. means comparing what other sources say about an unfamiliar site instead of judging it only by its presentation. Search for the author or organization in other reliable sources, check whether independent sources corroborate important claims, and follow citations back to the underlying evidence.
For example, a company webpage may report that its new study-skills app improves grades. The report may be relevant, but the company’s financial interest matters. Check how the study was conducted, whether its results are available, and whether independent researchers find similar effects. The webpage might support a claim about what the company says, but its claim alone is not proof that the app works.
Synthesizing research into a
A is a critical, organized account of research related to a defined topic or question. It does more than summarize sources one by one: it compares studies and explains how their findings fit together.
As you read, record each source’s question, methods, participants or materials, principal findings, , and to your topic. Then group sources by shared themes, methods, populations, time periods, or contrasting conclusions. A can help: place sources in rows and key themes or features in columns to make patterns and disagreements easier to see.
For example, studies of whether short classroom movement breaks improve students’ attention may not produce the same pattern across measures. Studies using teacher observations might report improvement, while studies using standardized attention tests show mixed results. Rather than listing each study separately, describe the pattern and consider whether differences in measures, age groups, or study designs help account for the variation.
A useful synthesis distinguishes among:
: findings point in a similar direction.
: findings conflict or differ in strength.
: differences in methods, samples, settings, or definitions may help explain varied results.
: weaknesses or boundaries affect how confidently findings can be applied.
Identifying and checking research gaps
A is an important question, population, setting, method, or time period that existing research has not adequately addressed. Gaps may be conceptual, methodological, or empirical; existing work may also be outdated.
Look for recurring , underrepresented groups or settings, conflicting results, concepts researchers define differently, and questions authors recommend for future study. Then check whether the apparent gap is genuine: search more than one relevant database or source collection, try alternative terms, and follow references and citations. A lack of results in one search may reflect narrow wording or limited coverage rather than an absence of research.
Not every gap is worth pursuing. Ask whether addressing it would clarify knowledge, matter to a field or community, and be feasible to investigate responsibly. State the gap precisely and explain how the reviewed evidence supports that conclusion.