Secondary research begins with evidence already available. That may include published studies, official statistics, earlier internal research, operational records, or other material collected before the current investigation. Its purpose is to establish what can already be learned and where an important gap remains.

Nielsen Norman Group’s introduction to secondary research describes its role in understanding a problem and the work that preceded it. The distinction from primary research concerns the source and use of data, not an automatic ranking of quality.

Search for an answer to a defined question

Suppose a team is considering a service for people arranging repairs at home. An initial review might examine existing work on scheduling, access, trust, and payment, alongside the organisation’s support records. A question such as “What prevents customers from being ready for a visit?” gives the review a more useful focus than a broad search for industry trends.

Record the sources and search terms, and follow important claims back to their original evidence. Several articles quoting the same survey are one underlying source, not several independent confirmations.

Internal material deserves the same scrutiny as published work. A previous study may be highly relevant, or may concern an audience and product version that differ from the current decision.

Evaluate fit as well as credibility

Check who produced the material, why, when, and through what method. Examine the population, definitions, questions, and limitations before using a number or conclusion.

In the illustrative repairs project, a survey of property managers may not describe tenants’ experience of arranging access. It can still be useful if that difference is preserved. A national estimate may provide context while offering little guidance on a particular booking interaction.

Distinguish an absence of evidence from evidence that a problem does not occur. A support archive may be silent because people never contacted support or because the relevant category was not recorded.

Turn the review into a useful next decision

Summarise what the evidence supports, where sources conflict, and what remains uncertain. Insight mining can help when the relevant material is inside an existing research archive.

Sometimes the review is enough for the decision. Otherwise, it should make primary research more focused by identifying the audience, context, or detail still missing. Keep source links and the search scope available so the next person can understand both the conclusion and the ground it covers.