Introduction and Hypothesis

This experiment evaluated the 3 input devices most commonly used for notebook computers. These devices consisted of the AccuPoint, TouchPad, and the TrackBall. While extensive research have been conducted analyzing the performance of various computer input devices, little attention was given to the specific input devices used in notebook computers. This experiment evaluated the speed, accuracy, and subjective preference of these 3 notebook computer input devices. Our subjects were familiar with computers and use the standard mouse as their primary input device source.

Our hypothesis was that for users most familiar with the standard mouse, the TrackBall will show optimum performance (speed and accuracy) as well as rate highest in subjective preference. The hypothesis was drawn from the fact that the TrackBall consists of the similar ball-rolling structure as in the standard mouse. Subjects familiar with the rolling action would find the Trackball's manipulation similar, resulting in optimum performance relative to the AccuPoint and the TouchPad, neither of which hold similar structural qualities.

Independent variables

The independent variable for this experiment was the type of notebook computer input device used. Particularly, we analyzed the performance and subjective preference on the AccuPoint, TouchPad, and TrackBall.

Dependent Variables

The main dependent variables measured were speed and accuracy upon completing the tasks, and subjective preference.

The speed was measured in seconds from the beginning of the task until each target was deleted. The stopwatch started at the initial movement of the cursor and ended when each target was deleted.

The accuracy variable was measured by recording the number of errors the subject encountered during the performance of the tasks. An error was recorded when the subject:

 

• Highlighted any portion outside the target 
• Deleted any portion outside the target 
• Selected the target partially 
• Selected more than a single line at any time

Subjective preference was also measured through the use of a questionnaire the subjects completed after performing the tasks on all 3 input devices. The questionnaire included rankings of the features and the different aspects of usage. Also, the questionnaire included free response that allowed the subjects to give feedback on any or none of the devices.

Statistic data were recorded in the following format.

	Accupoint	TrackBall	TouchPad
Total Time (mean)	.	.	.
(std dev)	.	.	.
Number of Errors(mean)	.	.	.
(std dev)	.	.	.
Subjective Satisfaction (mean)	.	.	.
(std dev)	.	.	.

Pilot study results

The pilot study was conducted with two subjects, both College students of different majors. During the pilot study, we ran into numerous problems that we had to address before conducting the actual experiments.

More specific instructions and demonstrations proved necessary when subjects tried to press the AccuPoint with more force (as if to act as the button) when a button was what was needed to be used. Also, when the TouchPad was used, a user insisted she wanted to use both hands. We decided not to allow this option because the TouchPad was not designed for such manipulation.

In respect to the layout, we had to change the text to fit on all notebook computer screens without having subjects scroll. Also, we learned that different notebook computers have different keyboard layouts, so we had to distinctly show the subjects where the delete button was located.

Also, at one point of the experiment, the computer froze for a while as it started "thinking." This ruined an accurate measure of speed since the experiment was interrupted. To eliminate this from happening, we ensured that the text file was the only application open during the experiment.

Lastly, there was confusion with some questions on the questionnaire. Some questions were added, other deleted. Typos were corrected.

Subjects

Fifteen subjects participated in this experiment, 8 male, 7 female. The subjects consisted of University of Maryland students from a variety of majors (i.e. Business, Spanish, Education, etc.), University of Maryland staff members, as well as individuals outside the university. The ages ranged from 16 to 26. All of the subjects had moderate to high computer experience and use the standard mouse as their primary input device.

Materials

The main materials for the experiment were the 3 input devices. The AccuPoint device was part of a Toshiba 435CDS notebook computer running on a Pentium 120 processor. The TouchPad device was on a Compaq Presario P155 and the TrackBall was on a Compaq LITE 4-25.

A text file was built consisting of textual targets in various positions. Fourteen targets consisted of the word "Delete." Each subject was given this text file and asked to delete all the targets with each of the input devices.

A questionnaire was also filled out by all subjects at the end of the session. Subjective preferences were measured in ratings from 1 - 5, 1 being strongly disagree, and 5 being strongly agree for each input device. Also, included was a free response section that allowed the subjects to express difficulties, suggestions, and features they enjoyed. (see appendix for full questionnaire)

The only training given was to explain the task and introduce the use of the 3 input devices. We demonstrated 2 deletes with each of the input devices to show the subjects how to manipulate the devices. In addition, demonstrations of each of the errors were performed. We allowed the subjects to practice to familiarize themselves with the task. To avoid the possibility of the subjects adapting to any input device during training, the subjects used the standard two-button mouse during practice (limited to 2 minutes) . These training procedures ensured the subjects were familiar with the tasks but not the devices.

Procedures and problems

The experiments were conducted in various locations. Several of them were conducted in residential atmospheres while most of took place in an office in the Lefrak building of the University of Maryland. This was done for the convenience of the subjects.

When the subjects arrived on location, the training session began (see above), followed by the opportunity to ask any questions. The subjects were told they were being measured on speed and accuracy.

Each subject performed the tasks on the 3 different input devices in rotating order. This was to ensure that the last input device used would not perform better based on the fact that the subjects became more familiar with the task after already performing it with the previous 2 devices.

Upon completing the task on all 3 input devices, the subjects were given an untimed questionnaire and were told to answer as thoroughly as possible. We decided to provide the subjects with the questionnaire after each task was completed, so they could answer the questions and rate the devices in respect to their experience with each input device.

Administration

Two experimenters were present in each test. One conducted the experiment, performed the demonstrations, presented the tasks, while the other measured the task execution times and error rate. When the tasks started, the experimenters recorded errors without notifying the subject so as not to make the subject feel uncomfortable or discouraged. While the subjects filled out the questionnaire, the experimenters left them alone and gave them an unlimited amount of time.

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