Guide · Content
Case Study Writing: How to Make One Buyers Trust
Case study writing is the craft of telling one client story so a buyer can check it and believe it. This guide gives a six-part structure, a simple permission note and a way to report numbers you can prove.
What a good case study does
A case study is a short story about one client, one problem and one result. A buyer reads it to answer a simple question: can this agency do for me what it did for them?
That is why trust matters more than polish. A case study full of big claims and no proof makes a careful buyer doubt everything else on your site. A plain one, with a clear problem, real steps and honest numbers, does the opposite.
Good case study writing also has a narrow job. It does not try to show every service you sell. It shows one piece of work well, and it lets the reader judge for themselves.
A six-part structure you can reuse
Most strong case studies follow the same order. Use these six parts and you will rarely get lost.
- The client. Who they are, what they sell, and how big they are, in one or two lines.
- The problem. What was not working, in the client's own terms. Keep it specific, such as "few online enquiries" rather than "weak digital presence".
- The goal. The result you both agreed to aim for, and how you would measure it.
- The work. What you did, in the order you did it. Name the tools and the time it took.
- The result. The numbers, with the dates they cover and where they came from.
- What came next. What the client did with the result, or what you would do differently.
Put the result near the top as a one-line summary, then let the rest explain it. Busy readers often stop after the first screen.
Get permission before you write
A case study uses facts that belong to your client. Their name, their sales figures and their quotes are not yours to publish. Ask first, and ask in writing.
A simple permission note should say:
- Which facts you plan to use, such as the client name, traffic, leads or revenue.
- Where the case study will appear, such as your website, a pitch deck or an award entry.
- That the client may read the final draft before it goes live.
- Whether the client wants to be named, or described only by sector and size.
If a client says no to a name, you can still write an unnamed case study. Say plainly that the client is unnamed. Do not invent a client or blend two clients into one story.
Quotes need the same care. A quote from a client must be something they really said, about their own experience. Do not polish it into words they never used.
Sources: ASAS, Singapore Code of Advertising Practice page; ASAS, Singapore Code of Advertising Practice, 3rd Edition (February 2008)
Report numbers you can prove
Numbers make a case study believable, but only if you can back them up. Singapore's advertising code speaks to this directly. Its guidelines say claims about matters of objectively ascertainable fact should be capable of substantiation. They also say advertisers and agencies must hold that proof ready to give the Advertising Standards Authority of Singapore (ASAS) on request.
A case study on your own website works like marketing, so it is wise to follow that habit. Before you publish any figure, check four things:
- Source. Which report or tool did the number come from, such as an analytics account or a sales ledger?
- Period. Which dates does it cover? "Leads up 80%" means little without a start and end.
- Baseline. What was the number before you began? A rise from 5 leads to 9 is real, but it is small.
- Cause. Did your work cause the change, or did a season, a sale or a new product help? Say so if other things played a part.
Keep a file with the proof for each case study. If anyone asks where a figure came from, you can answer in a minute.
Sources: ASAS, Singapore Code of Advertising Practice, 3rd Edition (February 2008)
Write it so people trust it
Use short sentences and everyday words. A buyer may not know the jargon, and a plain case study is easier to believe.
These habits help:
- Show the numbers you can prove, and leave out the ones you cannot.
- Include something that did not go to plan. A small setback, told honestly, shows the reader you are not hiding anything.
- Use real client words only with permission, and keep them short.
- Avoid words like "best" or "number one" unless you can show who said it and how it was measured.
- Do not promise that the next client will get the same result. Say what happened here.
The same code also warns that a testimonial should be genuine and based on the person's own experience. It says an unusual result should not be used unless the advertiser can show it matches what an average customer would expect. So if one client had a very lucky year, say that it was an unusual case.
Sources: ASAS, Singapore Code of Advertising Practice, 3rd Edition (February 2008)
A quick checklist before you publish
Run through these questions with the client's name on the page and a second reader beside you.
- Does the client know the page is going live, and have they approved it in writing?
- Does every figure have a source, a date range and a starting point?
- Is the problem described in the client's terms, not just yours?
- Does the story say what you did, step by step?
- Is the one-line result near the top, and is it true?
- Would the client be happy to read it aloud to a stranger?
If the answer to any of these is no, fix that part first. A case study that waits another week is better than one that has to be pulled down later.
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