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A Comparison of the Usability of a Laptop, Communicator, and Handheld Computer

Piia Suomalainen, Leena Korpinen, and Rauno Pääkkönen

Journal of Usability Studies, Volume 5, Issue 3, May 2010, pp. 111 - 123

Article Contents


Discussion

The following sections discuss the evaluation of methods and a comparison between devices.

Evaluation of methods

In recent years the use of laptops, communicators, and handheld computers has increased.  The three mobile devices are quite different, but people often do the same tasks with them. We thought that the laptop is a well known and quite general device so we used it to compare to the other devices. The laptop is larger and heavier than a communicator and handheld computer. If workers can do the same tasks with communicators that they can do with laptops without ergonomic problems, then they do not need to carry a laptop with them, for example, on the trips.

We did not randomize the devices for participants because we wanted to start with the most well known device—the laptop. We thought that starting the tests with the most familiar device (laptop) would help put our subjects at ease. Our results show that it was easier for subjects to type using the laptop (fewer typing mistakes per subject), but harder to make calculations on the laptop (subjects did not complete all of the calculations). Calculations were easier to complete using the handheld computer and the communicator, but typing tasks were harder to complete using these devices (higher typing mistakes per subject).

The length of one typing test or calculation test was only 5 minutes, which is quite a short time. However, because each subject completed six tests and answered five questionnaires the time could not be longer. Longer testing sessions can cause test fatigue.

We did not videotape the subjects because we felt it could influence the test situation and possibly cause the subjects to make more errors. However, it would have been easier to analyze the subjects’ work posture if we had videotaped the test sessions.

As with all tests performed with human subjects, each person brings his or her own biases, interpretations, and experiences that can influence how the usability of a device is rated and how ergonomic-based questions are answered. Also, some subjects may not understand the questions in the same way. For example, the word “ergonomic” can have a variety of meanings for different people. We did, however, give the subjects a research notice describing the test situation before tests, but it did not specifically include a description of the term “ergonomic.” We also felt that it was possible that our subjects may have interpreted the original scale incorrectly because often the larger number (5) is the most severe of the options. (The original scale was from 1 to 5, with1= very much stress, 2= fairly much, 3= pretty much, 4= pretty little, and 5= very little stress.) We decided to remedy this mistake in the analysis portion of our research by reversing the order of the scale, i.e., 5 = very much stress, 4 = fairly much, etc.

The 25 subjects were quite young, which may have affected our results. The results may be different if the subjects were older. However, our comparisons were based on only these subjects so the age of our subjects would not be a very important factor. Also, this age group often represents the potential users for these devices.

Another factor that might have influenced the results was the size of our test group. A larger group may have provided different results.

Comparison between devices

Our test results revealed that the subjects felt that the handheld computer and laptop had a better ergonomic design than the communicator. For all devices, our researcher observed a work posture that placed most of the stress load on subjects’ backs. In addition, all devices placed some work load stress on some parts of subjects’ upper limbs. The communicator and the handheld computer caused stress in the subjects’ eyes, which is easy to understand because communicators and handheld computers are quite small and the text is quite small too.

In addition, based on the question “Did you feel any stress in any part of your body when working with the devices?” subjects felt the laptop caused the most stress on their necks as compared to the other devices. Subjects felt the communicator caused the most stress on their backs as compared to the other devices. Moffet et al. (2002) mentioned in their conclusion that greater physical (muscular and articular) constraints seem to be imposed on the head-neck and wrist segments in laptop situations.

In the typing tests, the subjects wrote most with the laptop and least with the handheld computer. Using the Friedman’s 2-way ANOVA differences between all pairs (laptop–communicator, laptop-handheld computer, and communicator-handheld computer) were significant (p < 0.05). However, the laptop was most well known to subjects, so this could have influenced the results. In the calculation tests, the differences were not significant. Due to technical difficulties three subjects had to complete the writing test with the handheld computer, but their data does not differ from the common trend.

In our study, the subjects used the devices on tables. In general, people work with mobile devices in a variety of places and positions. For example, when a person travels a table might not be available so that person would use the mobile device in his or her lap. It is possible that the results of this study could be different if other environments were tested. In the future it would be interesting to study the same devices in different work environments and situations. Stress was highest with communicator and handheld computer, and lowest with laptop. The usability was vice versa, and thus usability and stress can be combined to be correlated. This could be one research area to develop in the future.

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