Basically, you will need to convince me that you have spotted a usability problem. To do that, explain what the problem is, who is affected by the problem, why it is a problem, and conclude with suggestions for addressing the problem.
If you want an approximate structure for the case study, translate each of the four steps into a paragraph of 100-150 words. This will automatically help you structure your argument. To further help you structure and write, summarise the key point you want to make in each paragraph in 2-3 bullet points, and then write out those bullet points.
Use a neutral, factual writing style, make sure you say where exactly the self-service machine is (Country, operator, location, e.g. the self-service till in the Quartermile Sainsbury’s), and use plenty of pictures to illustrate your points.
The word “figure” in the original task description is a term that covers anything that is not a table – pictures, diagrams, graphs, etc.
Make sure that you use enough pictures to help you make your point. It is all about explaining clearly what the one small problem is that you have identified. Typically, 1-2 pictures are enough.
The Open University has great advice on how to write a short essay.
When you explain who is affected by the problem, and why it is a problem, try as far as possible to link back to concepts and theories that we have discussed in the course – look at the “Understand” and “Remember” sections of the learning outcomes for inspiration. I’m also happy for you to throw in cultural or anthropometric aspects, if you like. However, make sure that you use the correct scientific terminology; when in doubt, refer to the textbook.
And, most importantly of all, go small!
Here are my marking criteria for the Case Study:
- Did you address all of the four steps?
- How well do you understand the aspect of design that you have chosen? range: not at all – publication quality
- How well structured and coherent is your argument? range: no argument – publication quality
- How clear is your writing? Range: incoherent, impossible to understand – brilliantly clear
Note that I am not marking you on grammar – as I have seen time and time again, you can be very clear and easy to understand despite making a few grammar mistakes.