Concurrent versus retrospective verbal protocol for comparing window usability
The measurement of software usability has become an important issue in recent years. Metrics of usability include time, errors, questionnaires, ratings, and results of verbal protocols. Concurrent verbal protocol, a method in which the user "thinks aloud" while completing given tasks, h...
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| Format: | Others |
| Language: | en |
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Virginia Tech
2014
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| Online Access: | http://hdl.handle.net/10919/39346 http://scholar.lib.vt.edu/theses/available/etd-09162005-115003/ |
| Summary: | The measurement of software usability has become an important issue in
recent years. Metrics of usability include time, errors, questionnaires, ratings,
and results of verbal protocols. Concurrent verbal protocol, a method in which
the user "thinks aloud" while completing given tasks, has been heavily
employed by software usability researchers who want to know the reason a
user is having difficulties. Possible problems associated with using concurrent
verbal protocol are (1) that verbalization may interfere with the processing
required to complete the task, and (2) that subjects may not be able to monitor
and express the information of interest to the researcher. A relatively new
approach which may avoid these problems is heavily cued retrospective verbal
protocol in which the user is presented subsequently with a representation (a
video tape, for example) which helps him recall his thoughts during the task
without interfering with task completion.
This research compared the performance of subjects while completing tasks
using both methods of verbal protocol. The verbal data collected by the two
protocol techniques was compared to assess any information differences due to
the methods of collection. No performance differences were found between the
two protocol methods. Reasons for this lack of degradation due to concurrent
verbalization are discussed. The kinds of information gathered were quite
different for the two methods, with concurrent protocol subjects giving procedural information and retrospective protocol subjects giving explanations and design statements. Implications for usability testing are discussed.
The two methods of protocol were employed in a comparison of two different
size monitors, a 30.48 cm diagonal and a 53.34 cm diagonal. The subjects'
performance, as measured by steps to completion, task completion time, and
errors committed, was compared across the two monitors. Subjects were
required to complete 12 tasks which varied in the difficulty of the windowing
required. Subjective data were also collected in the form of task difficulty
ratings, as well as a global measure of user satisfaction. These performance
measures and subjective measures were compared across protocol methods
as well as monitors. Performance data, as well as subjective data, indicate that
on tasks that do not require extensive windowing, there are no difference
between the two monitor sizes. As windowing difficulty increases, however, the
large monitor's advantages become apparent. Tasks with a high level of
wi ndowing difficulty are judged to be easier and require fewer steps on the
large monitor than on the small monitor. === Ph. D. |
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