3 Comparing and Assessing Sources

Start with the question

When several sources address the same question, do not decide by simply counting how many agree. Compare how each source was created, what it can show, and how well its evidence supports its claims. A source may be useful for one question but weak for another.

Assess each source

Assess sources by considering several related features:

• Purpose: Is the source meant to inform, explain, persuade, sell, entertain, or record an event? Who is its intended audience?

• Perspective: Who created it, and what did they experience or believe? What interests, assumptions, or limitations might shape the account?

• Expertise: Does the creator have relevant knowledge or access to the subject? The creator might be a qualified researcher, eyewitness, organization, or another informed person.

• Evidence: What facts, examples, data, documents, or firsthand observations support the claims? Can the evidence be checked against its original context?

• Reliability: Is the information accurate, relevant, and sufficiently current for the question? Does the source explain its methods and identify its evidence? Can important claims be confirmed elsewhere?

Purpose and perspective matter, but neither automatically makes a source unreliable. An advocate can provide accurate evidence, while a neutral-sounding account can contain errors. Evaluate particular claims and their support rather than relying on a source’s label or tone.

Match source type to the question

A primary source is a firsthand record, such as a letter, interview, photograph, government document, or original dataset. It can show what someone recorded, observed, or experienced, but it may be incomplete or shaped by the creator’s viewpoint. A secondary source interprets or analyzes information, often drawing on multiple primary sources; it may offer context, but its interpretation should also be assessed. Neither type is automatically more reliable: usefulness depends on the question.

For example, a local survey may provide direct responses when investigating what residents think about a new park. To assess how common those views are across the town, examine who was surveyed, how many people responded, when the survey took place, and whether the sample represents the town. An interview can provide vivid detail, but by itself cannot establish what most residents think.

Check claims and evidence

First identify each source’s claim and the evidence it offers. Then check whether the evidence actually supports that claim. Look for specific, checkable details rather than unsupported assertions; an explanation of where the information came from; evidence relevant to the question; acknowledgment of important limitations or uncertainty; and support from independent sources.

For charts and statistics, check what is being measured, the time period, the population or sample, and the original data source. Read axes and units carefully. A truncated axis or selectively chosen time range can make a difference appear larger or smaller than it is, so a chart’s visual presentation is not a substitute for examining the underlying data.

Reconcile agreement and disagreement

When sources agree, ask whether they rely on independent evidence. Several articles that repeat the same original report are not necessarily several separate confirmations. Trace important claims to their earliest available evidence and compare how each source uses it. Cross-checking can confirm facts, reveal missing context, or expose useful differences in perspective.

When sources disagree, first check whether they address the same question, people, place, and time period; define key terms in the same way; use the same evidence, methods, or samples; distinguish observation from interpretation; and have similar access, purposes, or perspectives. Differences in methods or definitions may explain a disagreement without implying a factual contradiction. For example, two reports may give different figures because one counts people who attended an event and the other counts tickets issued.

If sources make genuinely conflicting claims, seek original records or additional independent evidence. If uncertainty remains, state what is supported, what is disputed, and what cannot yet be concluded.

Apply the comparison process

Suppose a town newsletter says a reading program improved students’ test results, while an independent report says the evidence is inconclusive. Compare the sources rather than choosing based on their titles.

• Purpose: The newsletter may be promoting a town initiative, while the report may be evaluating its results.

• Perspective and expertise: Find out who wrote each source and what relevant knowledge or involvement they had.

• Evidence: Check whether results are presented, how many students were included, and whether there was a comparison group.

• Reliability: Look for methods, dates, and original data, and check whether other independent evidence supports the findings.

• Reconciliation: The newsletter may describe improvement among participants, while the report asks whether the program caused that improvement. These are different claims.

A careful conclusion would reflect the limits of the evidence: scores rose among participating students, but the available information does not establish that the program caused the rise.

Draw evidence-based conclusions

Compare sources by purpose, perspective, expertise, evidence, and reliability. Match each source to the question it can answer and verify important claims against independent evidence. Agreement can strengthen a conclusion when the evidence is genuinely independent; disagreement can reveal uncertainty or distinct aspects of the topic. Draw conclusions only as strong as the evidence allows.

• corroboration