A case study is written to win work, so it deserves the same scrutiny you would give any sales claim. Before you let one sway you, put a few plain questions to it. None of them needs inside knowledge; each can be answered from the study itself or by asking the agency.
- Is the client named, and did they agree to be? A result credited to an unnamed "leading firm" is impossible for an outsider to verify.
- Where did it start? A large percentage from a tiny base can describe very little real change.
- Which system counted it? Ask whether the client could open that report themselves.
- Were paid ads kept out? Advertising can lift almost any traffic or enquiry chart.
- Can you see what was done? A result with no record of the work behind it is hard to learn from, and harder to repeat.
It also helps to know what kind of number you are looking at. Rankings, impressions and changes shipped show the effort moving; enquiries and bookings show it paying off. Both are fair to publish, as long as each is labelled for what it is and nobody passes one off as the other. A study that blends the two, or reports only the flattering kind, deserves a second look.
Then ask how typical the result is. One standout client shows what is possible, not what is likely for a business like yours, in a market with its own competitors and its own starting point. Ask, too, how long the work had been running when the figure was taken, because a number recorded well into a campaign tells you little about its first few weeks.
Hold the studies above to the same standard, and do the same with every agency on your shortlist. A confident agency will welcome the questions, because its answers are the best evidence it has.