Data obtained from surveys of two samples of maritime crew members were studied for differences in self-reported sleep lengths and sleep problems. The data addressed both on- and off-duty variables. Statistical analysis of the data found that on-duty sleep length was shorter than off-duty sleep length for both groups. The two groups' responses to various sleep-problem items were significantly different. Most responses were below the scale mid-point. The differences between on- and off-duty sleep-problem items were not significant. Following a factor analysis, selected sleep-problem items were combined to form a composite Sleep Disturbance Scale. Using this composite measure, the correlation between the composite and sleep length was not significant. Overall, the results indicate that caution should be exercised before labeling shift workers as having "disturbed sleep" or suffering from "sleep disorders." The results do confirm the previous findings that shiftwork reduces sleep length on workdays.
As part of an effort to connect results of human factors testing with the needs of internal business clients, a usability testing program was created for smartphones to establish a link between usability metrics and business indicators of success in the marketplace. In addition to standard usability metrics of effectiveness, efficiency, and satisfaction (ISO, 1998), a measure of hedonics (Hassenzahl, Beu, and Burmester, 2001) was used. Of particular note was the use of the System Usability Scale (SUS) (Brooke, 1996) to provide a single measure of user satisfaction for all smartphones tested. Data from 54 studies involving 872 participants were analyzed to determine if usability metrics predicted marketplace outcomes. Results show that usability metrics are significantly correlated with indicators of business success and that the SUS accounted for most of usability's contribution. Discussion of these results, the value of SUS, and implications for usability professionals are discussed.
The present study examined how training difficulty interacts with individual differences in visual processing strategy. Participants discriminated between random polygon stimuli that varied both in both complexity and similarity. Individual processing strategies were categorized into either "holistic" or "analytic" strategy types based on the discrimination latency as a function of polygon complexity. Training difficulty was defined by the similarity of the stimuli being discriminated. Both strategy groups discriminated between similar ("hard" training) or dissimilar stimuli ("easy" training) and then between novel polygons in a transfer stage. Results showed that individual differences in processing strategy interact with training difficulty to influence performance on transfer to novel stimuli. The effect of training on transfer performance was greater for the participants with a holistic strategy than for those with an analytic strategy. The implications for training and display design are discussed.
Pratt and Sohn (2001) suggested that training context impacts those with a holistic strategy while training context does not influence transfer performance for those with an analytic strategy. The present research attempts to compliment and extend their findings by examining the role of complexity and how it interacts with individual differences in visual processing strategy. Participants were given a visual discrimination task in which they trained on one of four stimulus sets that varied in complexity and similarity and then transferred to novel stimuli. Stimulus complexity was defined by the number of points each stimulus had. Stimulus similarity was defined by the six levels of discrimination difficulty. Using methods described by Pratt & Sohn (2001), participant's individual processing strategy was extracted from a screening session prior to training. Participants were categorized as either “analytic” or “holistic” based on their response reaction time as a function of stimulus complexity. Those with an analytic strategy performed with greater accuracy in transfer as complexity level decreased; those with a holistic strategy performed with greater accuracy in transfer as complexity level increased. Graphical design and training techniques are discussed.
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