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MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

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Downloaded from http://www.everyspec.<strong>com</strong> on 2011-10-29T14:56:01.DOD-HDBK-791(AM)TABLE 9-8. HUMAN ERROR RATE ESTIMATE DATA (Ref. 22)EstimatedRatesActivity10 -4 Selection of a key-operated switch, rather than a nonkey switch. (The value does not include theerror of decision where the operator misinterprets the situation and believes the key switch is thecorrect choice. )10 -3 Selection of a switch (or pair of switches) dissimilar in shape or location to the desired switch (orpair of switches) assuming no decision error. For example, operator actuates a large-handledswitch, rather than a small switch.3 X 10-3 General human error of <strong>com</strong>mission, e.g., misreading label and thereby selecting wrong switch.10 -2 General human error of omission where there is no display in the control room of the status ofthe item omitted, e.g., failure to return a manually operated test value to proper configurationafter maintenance.3 x 10- 3 Errors of omission, where the items being omitted are embedded in procedure, rather than at theend as in the previous activity.3 x 10- 2 Simple arithmetic errors with self-checking but without repeating the calculation by redoing it onanother piece of paper.0.2-0.3 General error rate given very high stress levels where dangerous activities are occurring rapidly.the sooner this point is reached. Accordingly, some of the 2. Noise (discussed in par. 9-4.2)environmental elements that interfere with the normal 3. Temperature and humidity (see Chapter 10)sensory process or heighten stress require study and mea- 4. Acceleration. shock, and vibration (see Chaptersurement during engineering test (Ref. 3). Contributing 10)environmental elements are5. Toxicological, radiological, and electromagnetic1. Illumination (discussed in par. 9-4.1) hazards (see Chapter 10).9-16

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