What is usability Usability 1 effective efficient and

What is usability? • Usability (1): effective, efficient and satisfactory • Usability (2): Ease of learning (faster the second time and so on) Recall (remember how from one session to the next) Productivity (perform tasks quickly and efficiently) Minimal error rates (if they occur, good feedback so user can recover) High user satisfaction (confident of success)

What is meant by the usability of software by describing the characteristics of software that exhibits good usability. • Usable software does what it is supposed to do • Supports forgiveness or recovery so that users can correct their mistakes • Supports consistency so that what is learned in one part of the system applies elsewhere • Supports redundancy so that users can choose a method to suit their own style • Provides help so that users can learn

• Employs metaphors so that real world knowledge can be employed • Supports coherence, e. g. standards across a range of software • Provides feedback so that users know what the software is doing • Interface is intrusive so that users notice what the interface is telling them

The Gap between users and the software • • Software is not designed around tasks that users perform. Users find themselves unable to comfortably or effectively use the software.

Why does the gap exist? • Slogan. “It should work” is often the only slogan. Today, reliability or functionality alone is not enough. Usability needs to be high on the software house’s priorities because it impacts users’ productivity and overall satisfaction with the product. • Process. The software development process follows an engineering model with little or no concern for the product’s users. Users are neither understood nor involved in the design and evaluation of the software. • Approach. First, system internals are designed. Then, a user interface is “slapped” on it. The resulting user interface reflects the underlying mechanism. For the user who just wants to complete a task using the software, a user interface based on the task is more appropriate than one based on system internals. For this, the interface should be designed first—based on users’ tasks—and then the internals. • Skills. Good software design calls for interdisciplinary skills. Besides programming skills, we need skills in user-centered design, technical writing, and graphic design.

How do users react? • • Confusion. The software is too complex. It is not structured as users expect. Frustration. The software is inflexible and unforgiving. Users cannot undo incorrect actions. Panic. The software’s response time is too slow—just when the user is under tremendous pressure. Boredom. The software’s response time is slow and tasks are overly simplified. Incomplete use. Only some of the software’s functions or tasks are used. These tasks are often the easiest to perform. Indirect use. Managers who find the software hard to use, for example, get someone else to do it. Misuse or modification. Those who know the software well may change it to meet personal requirements that do not advance organizational interests. In this case, system integrity may be adversely impacted. Abandonment. The software is rejected by managers and other users who have the discretion to reject it.

HCI vocabulary • • Visiblity, refer to notes Affordances, refer to notes Mappings, relationship between actions and controls. Mappings are said to be good if they appear natural and intuitive to the users. Constraints, limits the number of possiblities of what can be done with the objects. Feedback, let users know what their actions have achieved, through visual, auditory, haptic Tasks, users are goal directed (specific problems to solve), it means task to accomplish. Tasks are complex, decomposed into sub-tasks. User’s model /mental models, the model people have of themselves, others, the environment, and the things which they interact. People form mental models through experience, training and instruction. Interface metaphors combine a familiar domain with system structure to make a concrete user interface

The design model, the user’s model and the system image (Norman and Draper, 1986, p. 46)

Feedback, let users know what their actions have achieved, through visual, auditory, haptic

The affordance of objects Do these icon suggest how you use them? (a) Slider and (b) button icons

A Map of HCI

Norman’s model of interaction (to help understand the interaction between human user and computer) Norman’s Seven Stages of Action / Norman’s Execution. Evaluation cycle

Gulfs of Execution and Gulfs of Evaluation The relationship between the user and the system can be conceptualized in terms of the gulf of execution and the gulf of evaluation.

Gulf of Execution: Refers to the distance between the user’s goals and the means of achieving them through the system. (What is needed to transform intentions into an associated set of actions. ) The interface should therefore aim to reduce this gulf. Gulf of Evaluation: Refers to the distance between the system’s behavior and the user’s goals. (What is needed to interpret physical state of the system and to determine how well state matches up with intentions. ) The more effort that is required on the part of the user to interpret the presentation, the less effective the interaction.

Cognitive issues in Direct Manipulation(DM) Interaction Style • DM is an interaction styles that uses: a continuous representation of the objects of interest via a meaningful metaphor. rapid, incremental, reversible operations simple, ‘physical’ actions (Shneiderman, chapter 6) • E. g. Windows and Macintosh desktop user interfaces

• DM reduces the gulfs of execution & evaluation: * rapid, incremental, reversible operations encourages low-cost evaluation – good for learning & error correction, builds an accurate user’s model. * simple, ‘physical’ actions (interact directly with the objects) reduces gulf of execution * a continuous representation of the objects of interest via a meaningful metaphor. creates a ‘user model’ of the user interface – users can predict what will happen, reduces gulf of evaluation.

Cognitive issues in natural language processing / command line interaction styles • Reduces gulf of execution and evaluation?

• User Objects and User Actions User objects are the items users see (and interact with) on the software’s screen. Examples are windows, menus, and scroll bars. Figure 1 gives a list of user objects.

User actions are the interactions users have with user objects. An example is a mouse click a user performs to select an icon. User actions include the following: • Navigation; • Selection; • Keystrokes (entry, etc. ); • Direct manipulation (clicking, dragging, dropping, etc. ).

Interaction & Support information Interaction Information Labels and messages are called interaction information, essential for completing user-software interaction. Labels are required to identify user objects, messages are required to give feedback to users about a user action or a change in system status. For example, the option “Edit” in your word processor is a label. Here are some examples of user objects that need labels: • windows; • menu options; • fields; • commands. A message can be provided in different ways. It can be textual, graphical, audible, or a combination.

Support Information For effective use of a software system, we also need to provide user documentation to “clarify” the following three software usability components: user objects, user actions, and interaction information. user documentation, is categorized as online support and printed support. Online support information appears on the user’s screen. Some online support information elements are as follows: • README files; • Online manual; • Field Help; • Message Help; • Online tutorial; • Cue cards; • Demos; • Examples; • Web-based information elements. Printed support information printed in the form of manuals, cards, or foldouts. Some printed support information elements are as follows: • Guide; • Reference;

Table 1. 2 Molich and Nielsen’s Usability Principles With the Corresponding Information Components How information contributes to software usability Component 2. Speak the user’s language. The text should be expressed clearly in words, phrases, and concepts familiar to the user, rather than in system-oriented terms. Labels and messages Component 5. Feedback. The system should always keep users informed about what is going on, through appropriate feedback, within reasonable time. Messages Component 8. Good error messages. They should be expressed in plain language (no codes), precisely indicate the problem and constructively suggest a solution. Messages Component 10. Help and documentation. Even though it is better if the system can be used without documentation, it may be necessary to provide it along with Help. Any such information should be easy to search, be focused on the user’s task, list concrete steps to be carried out, and not be too large. Online and printed support information

References • • HCI by Jenny Preece HCI information by Steve Brewster Designing Web Interfaces by Michael Rees User-centered information design for improved usability by Pradeep Henry