Question

COURSE: Human Computer Interaction

Why is it important to understand tradeoffs between usability measures for various kinds of systems? Explain by describing usability motivations for Industrial systems and Life Critical systems.

PLEASE: I DON'T PREFERR HAND WRITING AND PICTURES.

Answer 1

• Before we understand the importance of tradeoffs in usability measures, let us briefly understand what is a usability measure and what do we do with it.
• Usually, a usability measure is used to determine how well a system has performed when compared to the goal that has to be achieved, in technical terms, it can be defined as a set of well defined criteria/measures that help to determine the effectiveness and usability of your UI.
• POINT TO BE NOTED:This process varies based on different user communities, user expectations and tasks.
• This observation requires to follow two steps in the evaluation process

1. Determine your communities and the set of tasks that you need to benchmark

2. Define precise objectives for each task and community. This will guide the evaluation process

Generally there are 5 Aspects of usability measures

1. Time taken to learn by a typical member of user community to learn how to use the UI in order to perform the defined tasks.

2. Speed of performance and the time it takes to perform the benchmark tests?

3. Rate of errors made by users when performing the benchmark tasks? (Note: This is related to “speed of performance”)

4. Retention of knowledge on usage of UI over time by the user

5. Subjective satisfaction of UI

IMPORTANCE OF TRADEOFFS:

Since it is not possible to be perfect in every aspect, likewise in usability measures, it's not possible to perform all the aspects efficiently.They cannot be performed equally well, and this inequality in performance of aspects is called tradeoffs.

For example:The use of shortcuts or abbreviations increases the time to learn but also increases the speed of performance.

Therefore it is necessary to determine the most important measures for a specific project.

Usability Motivation

well-designed UIs can bring great benefits to the user and other stakeholders.There are 5 distinct groups of systems/applications that each have distinct characteristics and that each provoke specific motivational aspects for usability:

1. Life-critical systems

2. Industrial and commercial applications

3. Office, home and entertainment applications

4. Exploratory, creative and collaborative applications

5. Sociotechnical systems

Description and characteristics of usability motivation in Life-Critical systems:

The examples of life-critical systems include: Air-traffic control, medical instruments, nuclear reactor control, etc.

Characteristics

• High costs are expected and accepted
• High reliability and effectiveness is a must
• Time-to-learn is commonly high
• High speed of performance and low error rates are crucial
• Subjective satisfaction is of less importance
• Retention is obtained by frequent use and intensive practice

Description and characteristics of usability motivation in Industrial applications:

The examples of industrial applications include: Banking software, inventory management systems, human resource management software , etc.

Characteristics

• Costs are a very important factor
• Reliability and operational efficiency is important but not as crucial as it is with life-critical systems
• Time-to-learn should be low (as it lowers the costs)
• Speed of performance needs to be high (faster operating speed potentially increases the organization’s profit)
• Error rates should be low (trade-off with speed)
• Subjective satisfaction is of less concern
• After an initial training period, retention is obtained by very frequent use