A user interface provides a way of communication between a user and a computer. Interface design, as the name suggests, refers to creating the model of user interfaces for some software. Before a user interface design is finalized, it needs to be evaluated in terms of quality.
Evaluation helps test whether the interface meets the set requirements or not. A design evaluation highlights problems before the design is sent for the final implementation.
Ideally, evaluation should not be left to the end of the design process. Instead, it should be a continuous activity where individual interface components are assessed during the design process.
The techniques to perform evaluation can be broadly divided into two categories:
Evaluations that require expert analysis.
Evaluations that require involving user participation.
Let's look at different methods of evaluation under these two broad categories.
Expert analysis is practical when the designer lacks the resources to involve users. Evaluation through inspection by experts can be done through the following methods:
A cognitive walkthrough involves the evaluators performing the sequence of actions for each task and evaluating their learnability and usability from the users' perspective.
In the heuristic evaluation technique, evaluators critique the interface design, keeping some usability heuristics or principles in mind. Learn more about heuristic evaluation in this answer.
A model-based evaluation involves assessing the interface using some models of design specifications. One such model is the GOMS model.
An evaluation can be found based on previous studies or existing studies and experiments regarding specific interface designs. The expert evaluators sometimes make use of these studies to assess the interface.
Following are a few evaluation techniques involving participation from actual users.
In the experimental evaluation technique, controlled experiments are carried out to test specific hypotheses regarding the interface design.
The observational techniques involve watching the users and recording their behavior to understand their thought processes while using the interface.
The query techniques include asking the user directly about their experience with the interface, such as interviews and questionnaires.
Monitoring physiological responses is a way to take physiological measurements of users while they are exposed to the interface and analyze them.
The evaluation aims to:
Assess the system's functionality: Evaluation should consider whether the system provides enough functionality to allow users to perform tasks efficiently. It also involves assessing the user's performance and effectiveness in using the system. If the system replaces a manual task, it must provide enough capability to perform it similarly or better.
Assess users' experience with the interface: This involves evaluating the user's experience of the interaction and its effects on them. The user experience can be assessed by considering aspects such as learnability, usability, and user satisfaction. User pain points must also be examined and avoided.
Identify specific problems with the interface: This is related to the system functionality and usability of the interface design. It involves inspecting those interface components which generate unexpected outputs and confuse the users.
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