CHI 97 Electronic Publications: Late-Breaking/Short Talks
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Internet Delay Effects: How Users Perceive Quality, Organization, and Ease of Use of Information

Andrew Sears
School of Computer Science
DePaul University
243 South Wabash Avenue
Chicago, IL 60604
+1 312-362-8063
sears@cs.depaul.edu

Julie A. Jacko
Department of Industrial & Systems Engineering
Florida International University
University Park
Miami, Florida 33199
+1 305-348-3036
jackoj@fiu.edu

Michael S. Borella
School of Computer Science
DePaul University
243 South Wabash Avenue
Chicago, IL 60604
+1 312-362-8063
mborella@cs.depaul.edu

ABSTRACT

In this paper we report the results of an investigation designed to determine the effects of Internet delays on users perceptions of ease of locating information, organization of information, quality of information, and navigation problems. The results demonstrated user sensitivity to delays. As expected, for text-and-graphics documents, shorter delays provoked more favorable responses. However, for text-only documents, the shorter the delay, the less favorably a document was viewed. The results indicated that users may prefer multi-media web sites but are unwilling to tolerate the substantial network delays often associated with delivering graphics, video, animation, and audio.

Keywords

Internet, WWW, delays, perceived usability

© 1997 Copyright on this material is held by the authors.



INTRODUCTION

The Internet has quickly become a major player in the quest for information. People readily employ the Internet as a tool for information retrieval because it can provide fast access to vast amounts of information from a multitude of sources. Companies are rushing to establish an on-line presence by creating corporate World-Wide Web (WWW) sites describing their organizations and products.

While the Internet is being used more frequently to provide or locate information, research has shown that users do not like to wait for information to arrive. One of the most common complaints about the Internet is that some documents take too long to retrieve. There are several causes of delays: Web servers, Web clients, network latency[1]. However, while perceived latency is a concern of the average user, the cause of the latency is generally considered irrelevant.

It is widely recognized that system response time (SRT), the time between the user's input and the computer's response, is one of the strongest stressors during human-computer interaction [2]. Assessments of the effects of SRT have been conducted for personal computer use in a variety of contexts. As early as 1982, researchers determined that SRT and SRT variability act in concert to increase the stress levels of some personal computer users [3]. With increased SRTs, users rate their general well-being as lower [4]. Also accompanying longer delays are self-reports of annoyance [5], frustration, and impatience [6].

Given the results of previous research on system response time delays and the fact that Internet users' continue to complain about response delays, we examined the effect of Internet delays on the perceived usefulness, organization, and quality of information acquired from the Internet.

METHOD

Given an established WWW site, a second text-only version was created. Subjects viewed one of the two versions while experiencing one of three levels of delay: short, medium, or long. The subjects were not aware that six different conditions were being investigated.

The delays were generated using a trace-driven simulation technique [7]. This technique is based on measuring real network delays, processing the resulting data, and using these results to drive an instrumented WWW server. Using this technique, documents are delayed different amounts of time based on a number of factors including document size and the WWW site being simulated. Although means and medians do not adequately describe the distribution of document delays, they do provide an estimate of the differences between the three conditions. The following table provides mean and median delays for individual subdocuments (HTML file, graphic, etc.) for the three delay conditions. The specific delays were modeled after three heavily used web sites insuring that the delays were representative of real-world conditions.

Delay Condition
Short
Medium
Long
Median (msec)3852210 3600
Mean (msec)5753500 6750

To compel the subjects to explore the web site in detail, they were presented with 20 tasks requiring retrieval of information at the site. Subjects were allowed an unlimited amount of time to peruse the site. Subsequent to site perusal, the subjects were required to respond to a series of questions. The questions were designed to gauge the effect of delay on the subjects' perceptions of ease of locating information, organization of the information, quality of the information, and navigation problems. The subjects responded on a Likert scale of 1 (strongly favorable) to 7 (strongly unfavorable).

RESULTS AND DISCUSSION

The following figure depicts the differences between text-only and text-plus-graphics documents for short, medium, and long delays. Users were sensitive to delays for both text-only and text-plus-graphics documents. As would be expected, for text-plus-graphics documents, shorter delays provoked more favorable responses. However, for text-only documents, shorter delays resulted in less favorable responses. For example, when subjects were asked about the site's quality of the information, documents that arrived quickly were viewed less favorably than documents that arrived after a substantial delay. This indicates that users may expect graphics if the site is fast, but appreciate the use of plain text when delays become substantial. As can be seen from the following graph, medium delays produced mixed results.

The results consistently demonstrate that subjects perceive text to become progressively less favorable as the delay becomes shorter. In contrast, documents incorporating text-and-graphics become more favorable the shorter the delay. The results are consistent with previous studies that showed user sensitivity to delays during personal computer use. However, this study is the first that establishes sensitivity to delays of different lengths in the context of Internet use. The results indicate that users may prefer multi-media web sites but they are unwilling to tolerate the substantial network delays that may be associated with retrieving the necessary graphics, video, animation, and audio.

REFERENCES

  1. Padmanabhan, V. N. & Mogul, J. C. (1995) Improving HTTP Latency. Computer Networks and ISDN Systems, 28, 25-35.
  2. Thum, M., Boucstein, W., & Kuhman, W. (1995) human-computer interaction. Ergonomics, 38, 1342-1351.
  3. Weiss, S. M., Boggs, G., Lehto, M., Hodja, S., & Martin, D. J. (1982) Computer system response time and psychophysiological stress. Proceedings of the Human factors Society 26th Annual Meeting, 698-702.
  4. Kuhman, W., Boucsein, W., Schaefer, F., & Alexander, J. (1987) Experimental investigation of pschophysiological stress-reactions induced by different system response times in human-computer interaction. Ergonomics, 30(6), 933-943. Planas, M. A., & Treurniet, W. C., (1988) The effects of feedback during delays in simulated teletext reception. Behaviour and Information Technology, 7(2), 183-191.
  5. Schleifer, L. M., & Amick, B. C. (1989) System repines time and method of pay: Stress effects in computer-based tasks. International Journal of Human-Computer Interaction, 1(1), 23-39.
  6. Sears, A., & Borella, M. S. (1997) WANDS: Tools for designing and testing distributed documents. Technical Report #97-01, School of Computer Science, DePaul University, Chicago, IL.


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