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Improving the Usability of E-Book Readers

Eva Siegenthaler, Pascal Wurtz, Rudolf Groner

Journal of Usability Studies, Volume 6, Issue 1, November 2010, pp. 25 - 38

Article Contents


Methods

The following sections discuss the participants, apparatus, devices, and procedures used in this study.

Participants

Ten participants, 5 male and 5 female, were tested. Their ages ranged from 16 to 71 years (mean = 42 years). They were selected to represent the full range of possible e-reader users (with respect to subjective media experience, education, and subjective reading time per week). The average subjective media experience was 3.7 (scale from 1 to 6), and the average subjective reading time per week was 6.25 hours. Four participants had a high-school degree, two participants had a university degree, and four participants had completed an apprenticeship. All participants reported normal or corrected to normal vision and had no previous experience with e-readers. Participants gave written informed consent prior to participation. The study was performed in accordance with the latest declaration of Helsinki (WMA: Ethical Principles for Medical Research Involving Human Subjects, 2008).

Apparatus

Eye movements were recorded with an infrared video eye-tracking device (Tobii X120 Eye Tracker, Tobii Technology, Danderyd, Sweden). The system has a sampling rate of 120 Hz and a spatial accuracy of 0.5 degrees of visual angle. For each participant and trial, the system was recalibrated to assure best possible accuracy. Participants were allowed to move their head within a range of approximately 30 × 20 × 30 cm.

Devices

Five e-readers and one classic paper book were chosen for this study. The selection criterion was their availability in the Swiss market in June 2009. The five e-readers are listed below:

Figure 2 shows the e-readers used in the study.

Figure 2

Figure 2. The e-readers used in this study: (a) IRex Iliad, (b) Sony PRS-505, (c) BeBook, (d) Ectaco jetBook, and (e) Bookeen Cybook Gen.

The text material used in this study was the first chapter of a novel in German language (Querschläger, Silvia Roth, 2008). Every participant read the first 12 pages from the novel for legibility assessment.

Procedure

When the participants arrived at the laboratory, they were instructed about the aim and course of the experiment. The experiment started with a first legibility test. Participants had to read a segment of the text on all reading devices (five e-Readers and one classic paper book) while their eye movements were recorded. The reading devices were presented in randomized order, and the experimenter adjusted the font to the size most convenient for the participant (this was not possible for the classic book of course). Prior to each reading trial, a 9-point calibration procedure was performed to ensure the best possible measurement quality. Immediately after the first legibility test participants were interviewed, and they had to rate and give subjective preferences to each reading device.

Following the first legibility test, a two- hour usability-based task session took place. Participants had to perform small tasks on each of the six devices and rate the devices on different scales. Each participant had to perform the tasks and fill out separate questionnaires consecutively for each reading device. In this phase, participants worked individually because we wanted to create a general situation that was close to reality. The sequence of e-readers was randomized to control for order effects. Participants were allowed to use the user manuals and other documentations supplied by the manufacturers in the original device package. Participants had to complete the following five usability tasks:

  1. Open a book.
  2. Increase font size.
  3. Open a text in horizontal format.
  4. Open an audio-file.
  5. Open a picture.

For each task, participants had to answer whether they managed the task successfully or not. The time it took to complete the task was not noted because participants worked individually. After the small usability tasks were completed, participants were asked to rate (6-point Likert scale) the devices on the following criteria:

After completing the usability tasks and the ratings, participants filled out a questionnaire about usability and acceptance of the device based on Huang, Wei, Yu, Kuo’s (2006) questionnaire.

After the usability test, participants had a short break where refreshments were supplied. After the break, a second legibility test was administered. This second test was identical to the first legibility test with the exception that different text segments and different orders of e-reading devices were employed. Finally, participants were interviewed and asked to give subjective judgments in the form of ratings on a Likert scale with numbers matching the grading system as used by Swiss schools, ranging from 1 (very bad) 2 (bad), 3 (fail), 4 (pass), 5 (good), 6 (very good).

 

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