What is Peer Review?

Peer review is the check a journal runs before publishing a study, sending it to other researchers in the same field to look for problems. They judge whether the methods support the conclusions and can demand changes or rejection. It is a filter for obvious flaws, not a guarantee that the finding is true.

When a paper is submitted, an editor sends it to a few researchers who work on similar problems, usually unpaid and usually anonymous to the authors. They read the methods, ask whether the analysis really supports the claims, and recommend acceptance, changes or rejection. Changes is by far the most common answer. The process reliably catches visible failures: a missing control group, a statistical test that does not fit the design, conclusions reaching further than the data. What it cannot do is confirm the work happened as described, because reviewers see the write-up and not the laboratory. That is how invented data sometimes passes review and is withdrawn years later once others notice. Reviewers also never repeat the experiment, so peer review cannot tell you the result will hold when someone else tries it. So peer reviewed means somebody competent looked for the obvious errors, which is a floor rather than a verdict.

A building passing its plans inspection. The inspector reads the drawings against the code, checks the calculations and the specifications, and a design that fails genuinely has something wrong with it. But approval is granted on the paperwork, not the site, so it cannot tell you the builder poured the foundation the way the drawing says. That gets found out later, if at all.