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Considerable work is occurring in the development of decision aids, particularly for early event detection. The nature of these aids is such that there will be some degree of uncertainty regarding the actions that should be taken or the events that are implied.

Theoretical principles in situational awareness and empirical research show that there is a need to convey the degree of uncertainty in these probabilistic decision aids. For example, the early event detector may show a reactor runaway is about to occur, but a better aid also provides operators with how soon and how sure the system is of the assessment (i.e., how likely the event is to occur).

A group of researchers from the University of Buffalo looked at presenting probabilistic information in varying formats (Bisantz, A.M., Marsiglio, S., Munch, J., “Display Uncertainty: Investigating the Effects of display Format and Specificity”, Human factors, Vol. 47, No. 4, Winter 2006, pp 777-796).

While they used simulation of stock purchases, the implications for other systems is clear. The authors varied two factors (1) the specificity of the uncertainty (i.e., the certainty of the probability of the outcome) and (2) the presentation formats (e.g., numeric, encoded in symbols, verbal). Examples of the formats used in the study include the following:

Early Event Detection Examples

By varying the specificity, they found that how they presented the information (numeric, linguistic, iconic) was far less important than what was being conveyed. They came to three conclusions: (1) level of specificity impacts decision performance, as more ambiguous (less specific) probabilities were almost always treated as identical despite numeric differences, (2) while all subjects had threshold probability level for making a decision, the threshold was higher with increased specificity, and (3) specificity interacted with formats, such that graphical formatting of specificity (use of symbols or icons) resulted in more conservative actions than did numeric representations.

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| Alarm & Display System Analysis Overview | Alarm Management | Display Design | Alarm & Display Design Seminar | Beville Shape Calculator -Excel download | Alarm Distribution Estimator -Excel download |


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