Usability in Mobile phone Design

IMSE:8810Human Factor

Instructor: Dr. Linsey BakerStudent: Qiuyue Zhao

Outlines1. Introduction of usabilityWhat is usability?Usability in mobile phone designWhy is usability important?How do we do usability?

2. Discussion of papersPaper 1: A framework for evaluating the usability of mobile phonesPaper 2: Systematic evaluation methodology for cell phone user

interfacesPaper 3: Chinese character entry for mobile phones

3. Final conclusion

Usability: What is it?Usability can be a

attribute…

“How easy is this thing to use”

Usability is also a method

“How can I improve ease-of-use during

design”

we can therefore say…

“that ipod has great usability”

“that ipod was improved with usability”

Usability: What is it? Usability is a measure of quality It’s defined by six quality components:

EffectivenessLearnabilityEfficiencyMemorabilityError Prevention Satisfaction

Jakob Nielsen

Ben Shneiderman

Main mobile problemsThree features or limitations of mobile phoneSmall screensAwkward input, especially for typingProcessing power and available memory

Usability in Mobile phone design

Very heavy and

awkward

Smaller and more portable

The first mobile

phone with internal antenna

Full QWERTY keyboard

Multi-touch

Why is usability important in Mobile phone design? Usability is often associated with the functionalities

of the product If it’s difficult to use, people won’t buy If users get lost, they won’t buy If it’s hard to read or doesn’t answer user’s key

question, they won’t buy

How do we do usability?Early Focus on Users and Tasks

Know who the users areKnow what tasks the users will performKnow Which are most important

Empirical Measurement (Evaluation methods)Before starting the new design, test the old design. Test your competitors' designs

Iterative Designa cyclic process of prototyping, testing , analyzing,

refining a product or process

Usability Evaluation Methods(UEM)Analytic methods

Claims analysis Usability inspection

Heuristic evaluation Cognitive walkthrough

Empirical methodsThink aloudQuestionnairesUser interviewUser observation

Paper 1 :A framework for evaluating the usability of mobile phoneWhat is this paper about? Propose a structuralized usability evaluation model in order

to help practitioners identify and organize critical usability problems in a systematic way, understand the relationships among usability factors, and generate better design ideas.

Why?Pervious studies only focus on what could constitute the

usability factors, seldom organize them in a systematically.Most concerned with software products, not mobile

phone. So do not reflect the feature of mobile phone appropriately.

Something about Usability evaluation 1. Importance of usability evaluation2. Usability design problems:

Interface features design (task-independent) LUI: logistical user interface GUI: Graphic user interface PUI: Physical user interface

Users tasks design (task-dependent)

3. Usability Evaluation Methods(UEM)

Section 1: Research methodStep 1: collection and analysis of usability problems

First: classify usability problems into 2 categoriesTask-independent problems (interface design features)Task-dependent problems (user tasks)

Second: typically choose 28 mobile phone tasksThird: associate usability problems with mobile

phone tasks

Step 2: Identification of design features to be evaluatedWhat interface features to evaluate

Step 3: Evaluation strategy• How to evaluate interface feature

LUI evaluation GUI evaluationPUI evaluationTask-based evaluation

Section 1: Research method

Choose from four kinds of evaluations

Section 2:Proposed evaluation frameworkHierarchical model of usability factorsAim to

evaluate

Usability indicator

Usability criteria

Usability property

Usability indicatorsVisual support of task goals

Support of cognitive iteration

Support of efficient interaction

Functional support of user needs

Ergonomic support Physical aspect of interaction

Cognitive interaction

affective

Partial list of Usability criteria

Criteria checklist

Section3:Usability evaluation framework

Visual support of task goals

Conclusion This study developed an evaluation framework for

supporting usability practitioners to test the suability of mobile phones in an analytical way. A hierarchical model of usability Four sets of checklists A quantification methodAn evaluation process

Limitation Mapping relationship between evaluation areas and usability

indicators and its consequent evaluation items of the checklists.The goal-mean relationship need to be further examined

Paper 2: Systematic evaluation methodology for cell phone user interfaces

Object Develop a Systematic Evaluation Methodology for Cell Phone

User interface(SEM-CPU). SEM-CPU is a specifically designed to integrate five empirical methods into a laboratory-based test in order to evaluate cell phone UIs.

Three stages comprised to construct SEM-CPU

Stage 1

Stage 2

Stage 3

Stage1: Data collection in SEM-CPUFive method

Scenario-based task performance Benchmark tasks: tasks that reflect the realistic context of

use found outside of the laboratory Voice Activated Dialing (VAD) Short Messaging Service(SMS) Phone Book(PB)

Questionnaires (six usability attributes: icons clarity, text label, ease of use, ease of locating functions, quality of feed back and overall satisfaction.)

Retrospective think-aloud instead of concurrent think aloud

User observation for critical incidentsPost-task interview

Procedures of data collection

Stage 2: Data analysisStep 1: quantitative analysis

EffectivenessEfficiency SatisfactionLearnability

Step 2: qualitative data transformationQualitative Data logging(QDL) template

step 3:navigation flow diagram analysisStep 4:verbal protocol

Task completion time(s) Error rates

Task completion time and task completion ratio at repeated trails

Ratings of satisfaction

Task completion ratio(%)

An example of the table with the reorganized results of verbal protocol/critical analysis

Step 3: Navigation flow diagram analysis

No apparen

t disabilit

yCognitiv

e disabilit

y

Physical disabilit

y

Advantage: can identify the cause of usability problems

Stage 3: Data integrationTriangulation strategy

Example of design specification

Conclusion This paper present a systematic methodology,

called SEM-CPU, to evaluation cell phone UIs in laboratory-based testing. SEM-CPU guides usability engineers integrating five empirical methods to discover valid usability problems, and generate proper design specifications.• Efficiently conduct laboratory-based testing with multiple

empirical methods • Collect and measure necessary usability attributes• Identify determinants of usability problems • Generate proper solution

• Limitation• Quality analysis relies heavily on experts’ knowledge.

Paper 3: Chinese Character entry for mobile phonesObject A longitudinal experiment to evaluate

character entry performance using both objective and subjective measures for a new design and the existing cell phone keypad.

Background KnowledgeChinese is an iconographic languageTwo primary methods for entering Chinese

CharactersPronunciation-based methods (Pinyin)Stroke-based method Stroke: each stroke is written with a single action

Chinese Characters: the minimum functional unit.

Most characters are composed of two or more strokes.

character

strokes

Current stroke input methodA single stroke is used as the legend for each key to

represent the corresponding group of strokes

Problems:Failed to convey the necessary information to all users to

understand which strokes could be entered using each key. Select the wrong key Separate a single stroke into two or more pieces and attempt to enter

each piece separately Try to enter two or more strokes using a single key

Evaluation methodParticipants:

born and raised in China, lived in the US for more than 4 years. 24 volunteers(12 males, 12 females )

TasksText entry tasks: enter 5 sentences that were based on

headlines from a Chinese news website each of the 6 daysDistracter taskQuestionnaire

ProceduresPre-test on the first day6 days surveyNine-point scale Post-test on the last day

Dependent variablesEntry speed Character-level failures

Stroke-level accuracyOverall satisfactionFurther usage

Effectiveness of two keypad design

How well participants

understood the system

Thank you !