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The Role of Evaluation

Without doing some form of evaluation is impossible to know whether or not the design or system fulfills the needs of the users and how well it fits the physical, social, and organizational context in which it will be used. Evaluation is concerned with gathering data about the usability of a design or product by a specified group of users for a particular activity within a specified environment or work context.


When it comes to evaluation is important to consider:

  • The characteristics of the users (or the predicted users) of the product who take part in the evaluation (for example, experience, age, gender, psychological and physical characteristics).

  • The types of activities or predicted activities that the users will do. These may range from tightly specified tasks, which are defined and controlled by an evaluator, to activities decided by the users.

  • The environment of the study, which may range from a controlled laboratory situation to a natural work setting. If it is the latter, the study is known as a field study.

  • The nature of the artifact being evaluated, which may be anything from a series of sketches to a working software prototype or fully developed product.

Even in predictive evaluations, in which experts attempt to predict the usability of a system without directly involving users, evaluators take these same four aspects into account. They do this by drawing on their knowledge of the kinds of things that typical users would do and the sorts of circumstances in which they now typical users of the system will work. The kind of evaluation methods that are used in different evaluations will depend on the nature of the different components in our model and why the evaluation is being done. An evaluation in which the aim is to find out how the users work with current systems in their workplace will use quite different methods to an evaluation to compare two different layouts in a laboratory.



What do you want to know and why?

What do you want to know and why? Why do evaluation? The general answer to this question is: to find out what users want and what problems they experience because the more understanding designers have about users' needs, then the better designed their products will be. Without evaluation the products reaching consumers would be untried; they would reflect the intentions of the design team but there would be no study of the actual relationship between design and use. There are many times during design when designers need answers to questions in order to check that their ideas really are what users need or want. In this way, evaluation meshes closely with the design and guides the design by providing feedback. This kind of evaluation helps to form a product that will be usable as well as useful, and for this reason, it is said to be formative. In contrast, evaluations that take place after the product has been developed are known as summative because they are concerned with making judgments about the finished item, such as testing that a product conforms to a particular house style.



Reasons for doing evaluations

Four reasons for doing evaluations:

  • Understanding the real world. How do users employ the technology in the workplace? Can designs be improved to fit the work environment better? This kind of activity is particularly important during requirements gathering and then later for checking that prototypes of the system do fulfill users' needs.

  • Comparing designs. There are various occasions when designers want to compare two or more designs or design ideas. Comparisons may also be made of design specifications using techniques, discussed later, that do not involve users.

  • Engineering towards a target. The designers have a target, which is often expressed as some form of metric, and their goal is to make sure that their design produces a product that reaches this goal.

  • Checking conformance to a standard. Does this product conform to the standard? For example, is the screen legibility acceptable? Standard bodies have rigorous testing procedures to test that products conform to the standards that they have set.

Different kinds of information are needed for answering these questions, which are asked at different stages of design and development.



When and how do you do evaluation?

During the early states, evaluations tend to be done to:

  • predict usability of the product or an aspect of it;

  • check the design team's understanding of users' requirements by seeing how an already existing system is being used in the field.

  • test out ideas quickly and informally

Later on in the design process the focus shifts to:

  • identifying user difficulties so that the product can be more finely tuned to meet their needs,

  • improving an upgrade of the product

As a general rule, any kind of user testing is better than none. You will learn something valuable from even the most informal evaluations - watching a single user interacting with technology will provide feedback about its design. Different kinds of evaluations may be carried out at different stages of designs and for different reasons, but the evaluation is always to inform the design and to improve it at all stages.










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