Chapter 1

Usability of Interactive Systems

Outline

 

I.          Introduction

•         Design Science of Human-Computer Interaction (HCI) is interdisciplinary.

•         User Interface Design required for many diverse communities of users

 

II.        Usability requirements

•         Accessible; comprehensible; intelligible; idiot proof; available; and ready.

•         Less subjective measures  - U.S. Military Standard for Human Engineering Design Criteria (1999) :

•         Achieve required performance by operator, control, and maintenance personnel

•         Minimize skill and personnel requirements and training time

•         Achieve required reliability of personnel-equipment/software combinations

•         Foster design standardization within and among systems

•         Should improving the user’s quality of life and the community also be objectives?

•         Usability requires project management and careful attention to requirements analysis and testing for clearly defined objectives

 

III.       Goals for requirements analysis

•         Ascertain the user’s needs

–        Determine what tasks and subtasks must be carried out

•         Ensure reliability

–        Actions must function as specified

–        The system should be available as often as possible

–        The system must not introduce errors

–        Ensure the user's privacy and data security by protecting against unwarranted access, destruction of data, and malicious tampering

•         Promote standardization, integration, consistency, and portability

–        Standardization: use pre-existing industry standards

–        Integration: the product should be able to run across different software

–        Consistency:

•         compatibility across different product versions

•         use common action sequences, terms, units, colors, etc. within the program

–        Portability: allow for the user to convert data across multiple software and hardware environments

IV.       Usability measures

•         5 human factors central to community evaluation:

–        Time to learn: How long does it take for typical users to learn relevant task?

–        Speed of performance: How long does it take to perform relevant benchmarks?

–        Rate of errors by users: How many and what kinds of errors are made during benchmark tasks?

–        Retention over time: Frequency of use and ease of learning help make for better user retention 

–        Subjective satisfaction: Allow for user feedback

 

V.        Usability motivations

Many interfaces are poorly designed and this is true across domains:

 

VI.       Universal Usability

•         Physical abilities and physical workplaces

•         Cognitive and perceptual abilities

•         Personality differences

•         Cultural and international diversity

•         Users with disabilities

•         Elderly Users