Task Characteristics

The term control panel refers to the instrumentation console in a central control room through which process information is communicated to the process worker and via which the worker changes the state of the process. This category includes display elements such as chart recorders, bar indicators, dials, and modem VDU-based systems together with control elements such as buttons, switches, track balls and mice. The control panel is the human-machine interface (see Chapter 2) that has traditionally received the most attention from human factors specialists. 

The content and organization of the displayed information are of critical importance in inferring the state of the process and subsequently evaluating the effects of alternative courses of action. The following factors will determine the demands of the control panel on the attentional and memory resources of the workers. For detailed data on the design of the control panel, the reader is referred to standard ergonomics textbooks (e.g., Salvendy, 1987). 

The first questions to be considered when designing a control panel are what information is required and how much of it will be appropriate. Too little information may increase the amount of inference that the worker is required to make to predict the state of process parameters that are not directly displayed. This is especially important for emergency situations where the human information processing system is taxed heavily with many tasks. On the other hand, too much redimdant information can overload the worker. It is essential, therefore, that the information needs of the worker are identified through some form of task analysis and worker interviews. 

The relevance of the information to the process worker is another factor in design. This principle is often violated with the introduction of new VDU-based computer systems where information needed to assist computer scientists or production managers is mixed with information relevant for the safe operation of the plant. Clearly, some kind of structuring and prioritization will be necessary for the different users of the system. 

The issue of how controls and displays are identified on a control panel is usually referred to as coding. In the case of controls this can be achieved by techniques such as labeling, color, shape, location, or size. The relationship 

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Task characteristics (e.g., equipment design, control panel design, job aids)... 

This is the actual mental function required by the task that failed (see Figure 2.17). In the case study imder consideration the failure was at the Execute Action stage of the stepladder model, since the worker intended to operate the valve for reactor A, so there was no question of failure in the selection of actions. The connection with the task characteristics box indicates the fact that action is a fimction required by the task. 

O ReUly, C., Parlette, G., and Bloom, J. (1980), Perceptual Measures of Task Characteristics The Biasing Effects of Differing Frames of Reference and Job Attitudes, Academy of Management Journal, Vol. 23, pp. 118-131. 

Structure variables are the contextual parameters that may impact team processes and outcomes. We identified the following three dimensions within which the different structure variables could be classified organizational characteristics, team characteristics, and task characteristics. 

Task characteristics are factors that are specific to the problem assigned to the project team. We... 

While observation and shadowing can be used to develop task descriptions, surveys are particularly useful task-analysis tools when there is significant variation in the manner in which tasks are performed or when it is important to determine specific task characteristics, such as frequency (Jeffries 1997 Nielsen 1993). Surveys can also be used as a follow-on to further clarify task areas described via an interview. Focused observation, shadowing, retrospectives, and diaries are also useful for clarifying task areas. With retrospectives and diaries, an informant is asked to provide a retrospective soon after completing a task or to document his or her activities after several task events, the latter being a diary. 

Identified necessary goals, fimctions, and objectives to be met by system design Became familiar with practices, tools, and vernacular of work environment Characterized user profiles in terms of psychological characteristics, knowledge and experience, job and task characteristics, and physical attributes Acknowledged individual differences within target user population... 

Allow job task characteristics to define ergonomic interventions... 

Carayon-Sainfort, R. (1992), The Use of Computers in Offices Impact on Task Characteristics and Worker Stress, International Journal of Human-Computer Interaction, Vol. 4, No. 3, pp. 245-... 

This chapter deals with the analysis and decomposition of only the physical aspects of tasks. It is assumed that nonphysical resources are either available in nonlimiting quantities or are not crucial to task accomplishment While the compartmentalization of task characteristics tends to blur the natural connections among the various human performance resources, it is still the most pragmatic method available for task analysis. 

The imposition of different stressors, that is, a task characteristic or difficulty and a tool functionality (e.g., handling problem) lead to unknown strain effects. Moreover, different types of superpositions can occur (Luczak, 1982). When stressors are added, strain increases. Stressors that compensate each other reduce strain. Stressors ean be indifferent, sug-... 

Means and Explained Variance of Task Characteristics by the Psychophysiological Variables... 

Bryson, M., Lindsay, P.H., Joram, E., Woodruff, E. (1986) Augmented word-processing The influence of task characteristics and mode production on writers cognitions. Paper presented to the Annual Meeting oi the American Educational Research Association, San Francisco, CA, April. 

Five aspects potentially stimulate adaptation organizational norms and procedures, task characteristics, ejqterience and routines, deliberate initiation and control of actions, and meta-cognitive activity. 

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