Usability is usually referred to software but is also relevant to any product. Usability is improved by shortening the time to accomplish tasks, it reduces the number of mistakes that are made or can be made, and also it makes learning time shorter and improves peoples satisfaction with a system.
Usability sets out the relationship between users and tools. If the tool is effective, it must give an opportunity to intended users accomplish their tasks in the best way. It can characterize computers, websites and other software. If the systems work, their users must be able to employ them in the most effective way possible.
From the user's perspective usability is important because it can make the difference between performing a task accurately and completely or not, and enjoying the process or being frustrated. From the developer's perspective usability is important because it can mean the difference between the success or failure of a system. From a management point of view, software with poor usability can reduce the productivity of the workforce to a level of performance worse than without the system. In all cases, lack of usability can cost time and effort, and can greatly determine the success or failure of a system. Given a choice, people will tend to buy systems that are more user-friendly.
Usability depends on a number of factors including how well the functionality fits user needs, how well the flow through the application fits user tasks, and how well the response of the application fits user expectations. We can learn to be better user interface designers by learning design principles and design guidelines. But even the most insightful designer can only create a highly-usable system through a process that involves getting information from people who actually use the system. Usability is the quality of a system that makes it easy to learn, easy to use, easy to remember, error tolerant, and subjectively pleasing.
There are many approaches to evaluation of usability that can be chosen. Such methodologies can be divided into two board categories: those that can gather different information from actual users and those that can be applied without the presence of actual users. You choose the method that depends on cost of evaluation, time constraints, cost of implementation, appropriateness to project and cost of training new users. Usability evaluations can be conducted at many stages during and after the design and development process. When choosing, it is very important to calculate the cost not only in terms of time and materials that can be involved but also in terms of the impact on the end-users, especially considering the cost of losing return to your website due to unusable design.
There are some methods:
1. Cognitive Walkthrough the approach that is based on breaking down and analyzing actions that user must perform to use the system of finish the task.
2. Focus groups can be useful for razing issues that may not come out during interviews.
3. GOMSan acronym that stands for Goals, Operators, Methods and Selection Rules.
4. Prototypinginvolves the development process of a system for testing purposes.
5. Task Analysisshows how the user-end uses software or site.
6. Usability Inspectiondisplays the system that is based on a set of usability guidelines.
7. User testingobserver actual users interacting with software or websites.
