Usability Evaluation Of Mobile User Interfaces Computer Science Essay

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The mobile phone has quickly developed from simple device to complex multimedia interactive system. Because of mobile phone technologies' development and the development of mobile memory devices, mobile phone's functionality has been extended to include digital camera, MP3 player, location-based service and digital multimedia broadcasting (DMB) system in recent years. Thus, the mobile phone has been defined as a common user appliance (Klockar, Carr, Hedman, Johansson, & Bengtsson, 2003). As the development of functions and features of mobile phone, usability is an obvious features of mobile phones as well as usability evaluation is also an important activity for developing the well usable mobile phone that should be structured throughout all the design life cycle phases.

Usability evaluation is the essential aspect of the application of mobile interface because it can assess users' feedbacks regarding the mobile interface application as well as it can bring a lot of benefits to the users. By virtue of usability evaluation, there is a way to fulfill the user needs and requirements regarding the mobile application. To determine the usability of users achieved regarding application of product, it needs to measure the satisfaction and performance of users who work with the product. ISO 9241-11(1998) mentions that usability is an important aspect in the products' design because it is directly related to the extent to which the users of products are able to work effectively, efficiently and with satisfaction. Moreover, the usability of the products or applications may be developed by integrating the features and attributes of knowing the benefit of users in a meticulous context of use.

ISO/IEC 9126-1 defines usability as "the capability of the software product to be understood, learned, used and be attractive to the consumer, when used under specified conditions". This definition is basically related with the product of software but it be provided to the mobile phones for considering specified features for mobile phones. Although usability is generally concerned with the mobile phones design attributes, it requires to be regarded with a developing property that is structured by complex interaction amongst the mobile phone user interface, user and task features and other environment factors (Jeongyun Heo, 2009). Particularly, there is five attributes in the usability: learnability, efficiency, memorability, errors, and user satisfaction. The usability evaluation is mostly based on these usability issues.

The usability of MobiTOP application is evaluated based on the three user interfaces which are List, Map and AR. The main purpose of evaluation is to identify how these three different user interfaces are useful for the users and how MobiTOP application is efficient for different users and different tasks. The usability evaluation can identify what users need, when they need and which user interfaces can provide user to be more useful and more satisfied. Furthermore, the usability evaluation can determine whether MobiTOP application is ease of use and easy to learn for users or not. Therefore, the usability evaluation is important for application development and evaluation is based on the following identified usability constructs including ease of use, efficiency, effectiveness, satisfaction and learnability.

To evaluate how much user interfaces are ease of use for users, not only expert users but also novice users must be familiar with interfaces of mobile application. Everyone should be able to use the application within the short period of time once the application is introduced to the users (Good, 1982). Particularly, the application must be easy to remember the interaction otherwise the users may confuse to use the application next time. The application of MobiTOP must be feasible for both novice users and expert users.

The evaluation of the application efficiency is based on the rate or speed of users interact with system accurately and successfully to complete the specified task within the specified time. Regarding the efficiency, usability will be developed by changing the interaction procedure so as to shorten the operation time. Efficiency can also identify the ability of user to achieve the complete task with the specified time. As the time taken will based on the task nature, it is feasible to make direct efficiency data comparisons only when the same task is performed (Bevan, 2006). Furthermore, efficiency is measured as the mean time taken by the users who successfully achieve a goal divided by the time taken by an expert (Bevan, 2006). Therefore, the efficiency of the application is one of the important aspects in the usability evaluation.

ISO 9241-11(1998) defines that effectiveness is accuracy and completeness, in addition, error-free completion of tasks is important in both business and consumer applications. The factors of effectiveness are the quality of solution and error rates. Effectiveness measures oriented toward the outcome of the user's interaction with the system are gaining attention in usability evaluation (Bevan, 1995). To evaluate the effectiveness of mobile application, effectiveness measure includes percentage of users frequency of successfully completing performing the task, percentage of goals time to complete a task rating scale for achieved; tasks completed per satisfaction and frequency of complaints completed tasks (ISO 9241-11,1998).

Satisfaction which is the user's comfort with positive attitudes towards the use of the system and user's satisfaction can be measured by attitude rating scales (Kirakowski & Corbett, 1993). ISO 9241-11(1998) mentions that satisfaction (defined as freedom from discomfort and positive opinions to the use of the application) is the users' response to interaction with the application and satisfaction can be identified by subjective or objective measures. The evaluation of satisfaction is depended on how much users satisfy after they are interacting with the mobile application interface and the interface of mobile application can make users be pleased or satisfied.

The learnability of system interface is defined as the degree to which its interfaces help the novice users to use the useful tasks of mobile quickly and improve knowledge in using the interfaces of system (Nielsen, 1993). The learnability of complex system as the users interact with system "efficient and error-free in short period" so finally the users are satisfied (Linja-aho, 2006). Learnability concerns the features of the interactive system that allows novice users to understand how to use it initially and then how to attain maximal level of performance (Dix et al., 2004). It is the easiness with which novice users can understand how to use the system initially and achieve maximum performance. For learnability evaluation, application of mobile interface is identified whether the application interface can provide the users easy to learn to use application or not.

For users based evaluation, users are invited to do the typical tasks with mobile application interface first meanwhile their behaviors are observed and recorded in order to identify design flaws that cause user errors or difficulties. During these observations, the time required to complete a task, task completion rates and number and types of errors are recorded. The usability evaluation is based on the survey results with qualitative and quantitative methods. These methods are constructed with 90 participants from different background in different places. The survey questions are concerned with the five attributes of usability regarding the three user interfaces (List, Map and AR) and the results are evaluated based on the usability issues which user interface is the most useful and ease of use for both novice and expert users.

Questionnaire for Usability Evaluation

According to the definition of usability, that is concerned with the attributes of the product that make it understandable, learnable, easy to use and attractive, questionnaire is required to evaluate the usability of mobile application interface. Based on the literature review of our paper, we constructed the questionnaires for usability evaluation and questionnaires are concerned with ease of use, error handling, efficiency, effectiveness, satisfaction and learnability.

The usability evaluation questionnaire is divided into three different sections. In the first section, demographic information regarding the participants' information is mentioned such as background education, gender and organization. Section 2 includes the general questions concerned with the usage of mobile phone application for example how often users use the mobile phone to talk or to send SMS and how often users use their mobile phone to take photo or video. In addition, the questions regarding how much users are familiar with the MobiTOP application and the usability construct for MobiTOP application. The questionnaire for usability evaluation is following:

Questionnaire Section A

General questions concerned with mobile phone usage

Questionnaire Section B

General questions concerned with purpose to use

Questionnaire Section C

Ease of use regarding

MobiTOP Features

Accessing annotation

Questionnaire Section D

Error Handling regarded questions

Questionnaire Section E

Efficiency regarded questions

Questionnaire Section F

Effectiveness regarded questions

Questionnaire Section G

Satisfaction regarded questions

Questionnaire Section H

Learnability regarded questions

Each usability construct has different answers such as "1: strongly disagree", "2: disagree", "3: neutral", "4: agree", "5: strongly agree". Each questionnaire has four tasks and the users need to perform the task and each task has two actions that are browse and search.

In section 3, there are three subjective questions. The first question of section 3 is regarding the user interface and users need to list the features they satisfied. Moreover, the second question of section 3 is that users need to list the features concerned with the user interface and application they are not satisfied. The third question is the users need to list the suggested development regarding the user interface of mobile application (Please refer to Appendix 1).

Background of MobiTOP Application

MobiTOP application uses the Google Open Source Android platform to run its application and it provides the collaborative annotation data and allows the users to use the three different MobiTOP application user interfaces which are List, Map and Augmented Reality (AR). MobiTOP application interfaces allow the users modify the desired range (1km to 10km) and the annotation number (e.g 10 to 50) shown in each user interface of MobiTOP application.

Although the three user interfaces illustrate the same user needed information, they show the information by different ways. For example, if user finds the location by map application, MobiTOP shows the user required information by map. Our paper represents about how we evaluate the three different user interfaces of MobiTOP application based on the survey results and we discuss the future works for application. We show the screenshot of MobiTOP user interfaces (Map, List and AR) in Figure 1, Figure 2, Figure 3 and Figure 4 respectively.

For Map Interface, MobiTOP can indicate the users the current location of mobile phone and can detect the sensor of GSP. In map interface application, user can find the annotations by using two ways (search and browse). MobiTOP shows the annotations on the screen and first user can search the required location by touching it on the map. MobiTOP provides the user needed information as message box. If user wants to get more information or detail information, user can click " view detail" box on the map interface. There is photos, distance from current location to destination, tags and location description in the detailed information. In fact, map interface can provide the users to get the detailed information easily and quickly.

For List Interface, MobiTOP shows the user required information as list so that the loading time of list interface is faster than the loading time of map interface. MobiTOP already displays the list of annotations one after another based on the current location. User can easy to find the required destination or information by browsing the annotation or filtering based on the tags words. List interface can only display the text-based information.

For Augmented Reality (AR) Interface, users can see their current location as real view and they can find the required annotation information easily as well. The augmented reality (AR) in MobiTOP application allows the users to view the surrounding areas of current location by using the mobile phone camera and overlays the loaded information on this view. The goal of Augmented Reality is to add information and meaning to a real object or place. The UI in the AR has the helpful radar to show 360° view of annotations' locations. The main advantage of using AR interface is that the users can search the direction of their destination location since the annotations are shown on the screen that is based on the current location of users.

MobiTOP application provides above the three different user interfaces (List, Map and AR) intend to the online real time searching and browsing function to find the annotation information. For map interface, MobiTOP can also support offline version and users are allowed to load annotations from anywhere in a map. Furthermore, the feature of filter annotations in the MobiTOP using appropriate keywords is available for search function in three user interfaces. The main purpose of MobiTOP application is that it provides the users to get the required annotation information easily and quickly as well as users do not need to spend long time to get their required information.