Abstract

As cell phones have expanded their functionality with enhanced mobile technology, use of cell phones has become complex. Although usability of cell phones has been improved by featuring hierarchical menu systems, designing comprehensible navigation in the menu hierarchy is still a major challenge to cell phone user interface (UI) developers as more diverse users are adopting cell phones. To develop an easy-to-use cell phone UI, an effective usability evaluation method (UE) is essential. While various usability evaluation methods (UEM) have been developed, laboratory-based usability testing produces high-quality usability data from actual users. Yet, the effectiveness of such testing can vary dramatically depending on what data is collected and how the data are analyzed. To provide a practical guidance for the effective laboratory testing, we developed a systematic evaluation methodology for cell phone user interfaces (SEM-CPU). SEM-CPU is specifically designed to integrate five empirical methods (scenario-based task performance, questionnaires, post-task interview, user observation, and retrospective think aloud) into a laboratory-based test in order to evaluate cell phone UIs. By following SEM-CPU, usability engineers should be able to (1) conduct laboratory-based testing with multiple empirical methods in an efficient way, (2) collect diverse but useful data to measure necessary usability attributes, (3) identify determinants of usability problems, and (4) integrate all usability data to generate proper solutions for the problems. Detailed descriptions of SEM-CPU are presented along with a case study where SEM-CPU was applied to a comparative cell phone usability test.

Keywords: Usability evaluation; Mobile phone; Cell phone; User interface design

Article Outline

1. Introduction

2. Characteristics of cell phone user interfaces (Cell phone UIs vs. Window-based UIs)

3. Cell phone user interface evaluation and usability attributes

4. Systematic cell phone user interface evaluation methodology (SEM-CPU)

4.1. Data collection in SEM-CPU

4.1.1. Task-based performance (Formal laboratory usability testing)

4.1.2. Retrospective think aloud

4.1.3. User observation

4.1.4. Questionnaires

4.1.5. Post-task interviews

4.1.6. Preparation of data collection

4.1.7. Procedures of data collection

4.2. Data analysis

4.2.1. Step 1: Quantitative analysis

4.2.2. Step 2: Qualitative data transformation

4.2.3. Step 3: Navigation flow diagram analysis

4.2.4. Step 4: Verbal protocol and critical incidents analysis

4.3. Data integration

4.3.1. Identification of problematic tasks and menu items

4.3.2. Identification of common navigation paths and user behaviors

4.3.3. Problem causality and design recommendation pool

4.3.4. Design specification development

4.3.5. Design guidelines development

5. Conclusion and discussion

Acknowledgements

References