June 2010 Edition
Computer Science Department, University of Cape Town
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This course is about the design and evaluation of interactive computer systems in order to improve usefulness and usability. What does design and evaluation mean and why are these activities important?
When a child builds a house out of bricks there is very little design. It is unlikely that the child has analysed requirements, drawn up plans (with alternatives) and selected tools and techniques to carry out the task.
Unfortunately, sometimes when an interactive system is built, designers fail to consider an essential aspect of the system – the human users. For successful interactions, there has to be explicit and well-thought out consideration of this human factor – usability needs to be designed into the device or system.
To achieve this, as we will see later in the course, there are a range of models, techniques and tools that can be used to construct the system. All of these methods attempt to centre the design on the user group (this is why the methods are collectively known as User-Centred Design or UCD).
Interactive system designers must understand their users. A design developed for one type of users might not be the best for another group. For example, think about a cash-dispensing machine. What would be a good interactive design for this sort of system? Unless you know something about the user group you will not be able to give a workable answer to this question.
Interactive system designers need to know their users if they are to build effective systems. User-centred design, then, involves really understanding the capabilities, limitations, needs and wishes of your user group.
Standard cash machines (ATMs) are designed for ‘standard’ users with no physical or mental impairments.
Imagine you are designing an ATM for Sue. Sue is 75 years old.
List out the possible physical and mental characteristics that Sue might have and that are relevant to the design of an ATM.
How would you design an ATM to better suit Sue?
Now look at the World Wide Web Consortium's advice designing Web sites for universal access.
A discussion of this activity can be found at the end of the chapter.
imagine a parachute designer has designed what he feels is the ultimate parachute: lightweight, can carry heavy loads, and very safe. He is so convinced that it will work that he does not test his product until it is has been built. Then, one day, he takes a plane to a high altitude and, putting his faith in the chute, jumps…
A good designer will not simply trust that his skill and experience will always produce designs that are highly effective. Evaluation is about testing to see if the interactive system has good usability and usefulness. There are two types:
Formative evaluation: it is not good enough just to test your system once it is completely built. Evaluations should be carried out all the way through the design and development cycle. The results of these evaluations should be used to guide the design.
Summative evaluation: once a system has been built then an overall assessment of its usability is needed. These tests should be done to validate aspects of the design (e.g., is the system as learnable as we specified?) and to test the acceptance of the system by the end-users (i.e., do the users like the system, find it easy to use etc?). If a company is buying an off-the-shelf system, it might carry out summative evaluations of all the products to see which is best.
In this course you will look at several evaluation methods and learn when and how they can be used appropriately.
Spend half-an-hour looking at examples of bad human factors design on Michael Darnell’s Web site.
Before reading why the design is bad, spend some time carrying out your own summative evaluation to spot the problems.
Choose 3 items examples that you found the most interesting and post your thoughts on the course bulletin board.
A discussion of this activity can be found at the end of the chapter.
What is the difference between summative and formative evaluation? Why are both needed in the development of interactive computer systems?
Answer to this question can be found at the end of the chapter.