A USABILITY EVALUATION MODEL FOR DIGITAL LIBRARIES

ABSTRACT

Usability is the extent to which a product can be used by specific users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use. The Nielsen’s usability model has been popularly used for system usability evaluation. This thesis introduces a modification to Nielsen’s usability evaluation model which was used to evaluate the usability status of digital libraries in tertiary institutions in Lagos State. The digital libraries used were that of University of Lagos, Lagos State Polytechnic and Federal College of Education, Akoka. This modified model incorporates four traditional attributes (Efficiency, Effectiveness, Satisfaction, Learnability) and two additional attributes (Discoverability and Cognitive Load) introduced by the researcher; these two attributes were introduced because they have been proven to be user centered attributes which will help in getting the users’ personal experience while using the software (digital library) unlike the existing usability evaluation models which were majorly system centered.

The digital libraries will be assessed using modified heuristic think aloud method. The study employed purposive sampling technique to select the three tertiary institutions that was used for the evaluation while Yaro Yamani formula was used to calculate the users’ population sample size of (40) for each of the institution. Six task based questionnaires were used to carry out test in collecting data for the study; they include: (i) Discover ability test, (ii) Cognitive Load test (iii) Learn ability test (iv) Effectiveness test (v) Efficiency test and (vi) Satisfaction test. The mean of each of the usability attributes were used to evaluate the usability status of the digital libraries of the selected institutions. IBM SPSS statistics version 21 was used to calculate the mean.

The result of the usability test carried out established that the digital libraries of the tertiary institutions in Lagos state were usable. It also indicated that the users of the digital libraries were satisfied with the use of the digital libraries in the investigated institutions. For the three institutions, discoverability has a mean of 14.65, cognitive load has a mean of 14.81, learnability has a mean of 16.21, effectiveness has a mean of 16.89, efficiency has a mean of 16.56 and satisfaction has a mean of 16.27. Usability results of the evaluated libraries showed that the digital libraries are: Effective, Efficient, Satisfactory, helps users to learn and the discoverability and cognitive load of the students are fast.

In conclusion, this study has successfully modified the Nielsen’s usability evaluation model by adding Discoverability and Cognitive Load to its constructs and this study has also contributed to literature. The modified Nielsen usability evaluation model is recommended for use to evaluate usability of other digital libraries in other tertiary institutions in Nigeria and Abroad. 

TABLE OF CONTENTS

Content                                                                                                                   Page

Title Page                                                                                                                i

Certification                                                                                                           ii

Dedication                                                                                                              iii

Acknowledgments                                                                                                 iv

Abstract                                                                                                                  v

List of Tables                                                                                                          ix

List of Figures                                                                                                        x

List of Appendices                                                                                                 xi

Chapter One                Introduction                

1.1               Background to the Study                                                                   1

1.2               Statement of the Problem                                                                   3

1.3               Objective of the Study                                                                       4

1.4               Research Questions                                                                             4

1.5               Significance of the Study                                                                   4

1.6               Scope of the Study                                                                             4

1.7               Methodology                                                                                      5

1.8               Operational Definition of Terms                                                         5

1.9               Organisation of Subsequent Chapters                                           5

Chapter Two               Review of Literature                                     

2.0               Introduction                                                                                        6

2.1               Definition of usability                                                                         6

2.1.1            Attributes of usability                                                                         6

2.1.2            Importance of usability                                                                       8

2.1.3            The role of usability in digital libraries                               9         

2.2               Usability Evaluation Models                                                              10

2.2.1            Usability in ISO 9126                                                                         10

2.2.2            ISO/IEC 9126-1                                                                                 11

2.2.3            Usability in ISO 9241                                                                         12

2.2.4            ISO 9241-11                                                                                       13

2.2.5            Dix et al usability evaluation model                                             14

Content                                                                                                                   Page

2.2.6            Nielsen usability evaluation model                                              15

2.2.7            Eason usability evaluation model                                             16

2.2.8            Enhanced usability evaluation model                                         17

2.2.9            Normative usability evaluation model                                        17

2.2.10          Modified Nielsen’s usability evaluation model                         18

2.3               Usability evaluation methods                                                             18

2.3.1            Card Sorting                                                                                       18

2.3.2            Open card sort                                                                             19

2.3.3            Closed card sort                                                                                  19

2.3.4            Cognitive walkthrough                                                                       19

2.3.5            Focus group                                                                                        20

2.3.6            Think aloud                                                                                         21       

2.3.7            Contextual Inquiry                                                                              21

2.3.8            Heuristic evaluation                                                                            22

2.3.9            Questionnaire                                                                                      23

2.4               Digital library                                                                                      24

2.4.1            Role of digital library in Education                                        25

2.4.2            Sources of digital library                                                                     26

2.5               Review of closely related work on usability evaluation              29

Chapter Three Methodology                                                     

3.0               Introduction                                                                                        33

3.1               Research Design                                                                                 33

3.2               Population                                                                                           33

3.2.1            UNILAG digital library                                                                      33

3.2.2            FCE. (T) Akoka digital library                                                            34

3.2.3            LASPOTECH digital library                                                              35

3.3               Sample size and sampling technique                                    36

3.4               Usability model design/development                                                 37

3.5               Method of data collection                                                                  39

3.5.1            Think Aloud                                                                                        39

3.5.2            Heuristic evaluation                                                                            39

Content                                                    &nb