Richard Cordes
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Publications by Richard Cordes (bibliography)
» 2001 «
Cordes, Richard (2001): Task-Selection Bias: A Case for User-Defined Tasks. In International Journal of Human-Computer Interaction, 13 (4) pp. 411-419
“Usability evaluations typically occur throughout the life cycle of a
product. A number of decisions and practical biases concerning the tasks
selected for usability evaluations can influence the results. A pervasive bias
is to select only tasks that are possible to perform with the product under
evaluation, introducing a subtle bias for the participants. One way to avoid
this problem is to employ user-defined tasks (UDTs) in usability evaluations.
In addition, having participants define tasks to perform in a product
evaluation allows a more accurate assessment of product usability. This is
because UDTs based on users' requirements and expectations should be relatively
independent of the functional capabilities of a product. However, there are a
number of methodological and practical issues that result from the introduction
of UDTs in a usability evaluation. The best approach is to design hybrid
evaluations using both UDTs and product-supported tasks.”
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» 1993 «
Weiler, Paul, Cordes, Richard, Hammontree, Monty, Hoiem, Derek and Thompson, Michael (1993): Software for the Usability Lab: A Sampling of Current Tools. In: Ashlund, Stacey, Mullet, Kevin, Henderson, Austin, Hollnagel, Erik and White, Ted (eds.) Proceedings of the ACM CHI 93 Human Factors in Computing Systems Conference April 24-29, 1993, Amsterdam, The Netherlands. pp. 57-60. Available online
“This panel brings together usability professionals throughout the computer industry to demonstrate and discuss their usability lab software tools. These tools are specifically designed to improve the data collection and analysis process for usability labs. Their capabilities range from simple to complex and the panel will not only discuss the benefits of using the tools but also share the lessons learned during the design and development process.”
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Cordes, Richard (1993): The Relationship between Post-Task and Continuous-Vicarious Ratings of Difficulty. In International Journal of Human-Computer Interaction, 5 (2) pp. 115-127
“A study was conducted that used continuous-vicarious ratings (CVRs) of difficulty to investigate how people make judgments of task difficulty. Twelve people performed five editing tasks using a text editor. After each task, the participants rated the overall difficulty they experienced in performing the task. They then viewed a videotape of their performance. While the participants were viewing the tape, they were asked to rate continuously the difficulty they felt they had experienced at that moment when performing the task. From this curve of difficulty over time, seven variables were obtained as possible candidates in predicting their overall task-difficulty ratings. It was found that the contrast between the maximum or peak of the continuous rating and the mean difficulty level best accounted for the post-task ratings of difficulty, followed by the time it took to perform a task. In other words, the more the peak difficulty stood out from the background average-difficulty level combined with the more time spent performing a task, the higher the participants rated their overall task difficulty. A three-variable (maximum difficulty, mean difficulty, and time) power-function model was developed that best predicted the post-task difficulty ratings. The terms in this model were statistically significant and accounted for 63% of the variability in the task-difficulty ratings. These results imply that human factors practitioners may be more effective focusing on and improving what people judge to be the most difficult aspects of an interface. Indeed, the results suggest that concentrating on other areas to improve an interface may actually cause an increase in perceived difficulty simply because the problem causing the peak difficulty has become more salient.”
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Cordes, Richard (1993): The Effects of Running Fewer Subjects on Time-on-Task Measures. In International Journal of Human-Computer Interaction, 5 (4) pp. 393-403
“There is a desire to streamline the development design process by conducting usability evaluations with fewer subjects. This study examined the impact of using fewer subjects on the accuracy and stability of the mean and median. Monte Carlo simulations were conducted to model the skewed task-completion times typically found in usability studies. The results showed that the mean was a more accurate estimate of its respective population parameter than the median and should be the preferred metric in usability evaluations. However, the mean cannot always be used because it will underestimate the population mean when there are missing data as a result of subjects exceeding time limits. Alternatively, it was found that the median tended to consistently overestimate the population median by as much as 10% in one examined case. The average 95% confidence limits of both estimates were quite broad, particularly for the smaller sample sizes. Based on these results, it was concluded that with reduced sample sizes (e.g., 5), we are not able to measure population parameters with either a high degree of confidence or, in the case of medians, with any accuracy. It was recommended that usability measurements take a back seat to usability testing when conducting tests with small sample sizes.”
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» 1982 «
Cordes, Richard (1982): Software Guideline Development: A Proposed Methodology. In: Nichols, Jean A. and Schneider, Michael L. (eds.) Proceedings of the SIGCHI conference on Human factors in computing systems March 15-17, 1982, Gaithersburg, Maryland, United States. pp. 82-84.
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Mar 17th, 2010
Changes to this page (author)
18 Feb 2010: Enabled abstracts to be shown on Richard Cordes's author page.28 Apr 2003: Added the author to the bibliography
