Activity task analysis

User requirements extrapolation from actual users activities In this category includes methods such as interviews, direct observation of activities, task analysis and task modelling. Interviews can be a very valuable and relatively easy-to-use and cost-effective method for user involvement early in the design process. The method can give interesting results if the future users sample is large and varied enough, and if all the facets of the users activities are explored. 

The terms job hazard analysis QHA) and job safety analysis (JSA) are used somewhat interchangeably. A variety of other terminology such as job task analysis (JTA), activity task analysis (ATA), and others are used depending on the industry and organization. 

At this point, a task analysis is performed. A "task" is defined as an activity oi performance (hat the operator sees as a unit either because of its performance character]stic.s or becau.se that activity is required as whole to achieve some part of the system goal. Only the tasks that are relevant lo the system safety are considered. A task analysis involves decomposition of each task into individual units of behavior. Unusually, this analy.sis tabulates information about each specific human aciiun. The format of such a table is not rigid - any style that allows easy retrieval ot the information can be used. The format reflects the level of detail and the type of task analysis performed. The analysis yields... 

The following techniques can be used to collect data about human performance in CPI tasks and provide input to task analysis methods described in Section 4.3. These data can include process information critical for the task, control strategies used by the workers, diagnostic plans etc. A distinction can be made among data collection methods that provide qualitative data (such as interviews, observations, and sources of documentation) and methods that can be used to measure aspects of performance (such as activity analysis, simulations, and information withholding). The latter methods can provide more precise data which can be quantified. 

Hierarchical Task Analysis commences by stating the overall objective that the person has to achieve. This is then redescribed into a set of suboperations and the plan specifying when they are carried out. The plan is an essential component of HTA since it describes the information sources that the worker must attend to, in order to signal the need for various activities. Each suboperation can be redescribed further if the analyst requires, again in terms of other operations and plans. 

A new area of research concerns exposure assessment for beryllium in the production of nuclear weapons at nuclear defense industries. A safe level of exposure to beryllium is still unknown. Potential explanations include (1) the current exposure standard may not be protective enough to prevent sensitization, or (2) past exposure surveillance may have underestimated the actual exposure level because of a lack of understanding of the complexity of beryllium exposures. Task-based exposure assessment provides information not directly available through conventional sampling. It directly links exposure to specific activity associated with contaminant generation and provides in-depth evaluation of the worker s role in a specific task. In-depth task analysis is being used to examine physical, postural, and cognitive demands of various tasks. 

Role delineation. The first step is to define the area in which certification is to be offered. This is done through a process called role delineation or task analysis. An expert panel of individuals in the proposed subject area develops a survey instrument to assess how practitioners working in the area rate the importance, frequency, and criticality of specific activities in that practice. The instrument is then sent to a sample of pharmacists who are practicing in that field. 

In collaboration with testing experts, the PTCB developed a national examination, the Pharmacy Technician Certification Examination (PTCE). The examination is designed to assess the candidate s knowledge and skill base for activities that are most commonly performed by a pharmacy technician, as determined by a national task analysis. 

Cognitive task analysis deals with how operators respond to tasks delegated to them either by the system or by their supervisors. Tasks is used here to designate the operations undertaken to achieve certain goals under a set of conditions created by the work system (Leplat 1990). CTA looks at several mental activities or processes that operators rely upon in order to assess the current situation, make decisions, and formulate plans of actions. CTA can include several stages ... 

The human factors literature is rich in task analysis techniques for situations and jobs requiring rule-based behavior (e.g., Kirwan and Ainsworth 1992). Some of these techniques can also be used for the analysis of cognitive tasks where weU-practiced work methods must be adapted to task variations and new circumstances. This can be achieved provided that task analysis goes beyond the recommended work methods and explores task variations that can cause failures of human performance. Hierarchical task analysis (Shepherd 1989), for instance, can be used to describe how operators set goals and plan their activities in terms of work methods, antecedent conditions, and expected feedback. When the analysis is expanded to cover not only normal situations but also task variations or changes in circumstances, it would be possible to record possible ways in which humans may fail and how they could recover from errors. Table 2 shows an analysis of a process control task where operators start up an oil refinery furnace. This is a safety-critical task because many safety systems are on manual mode, radio communications between control room and on-site personnel are intensive, side effects are not visible (e.g., accumulation of fuel in the fire box), and errors can lead to furnace explosions. 

Drury, C. G., Prabhu, R, and Gramopadhye, A. (1990), Task Analysis of Aircraft Inspection Activities Methods and Findings, in Proceedings of the Human Factors Society 34th Annual Conference, (Santa Monica, CA), pp. 1181-1185. 

Effective interactive system design thus comes from a basis in direct observation of users in their work environments rather than assumptions about the users or observations of their activities in contrived laboratory settings (Hackos and Redish 1998). Yet contextual tasks analysis is sometimes overlooked because developers assume they know users or that their user base is too diverse, expensive, or time consuming to get to know. In most cases, however, observation of a small set of diverse users can provide critical insights that lead to more effective and acceptable system designs. For usability evaluations, Nielsen (1993) found that the greatest payoff occurs with just three users. 

Observation during task activity or shadowing workers throughout their daily work activities are time-consuming task-analysis techniques, but they can prove useful when it is difficult for informants to verbalize their task knowledge (Jeffries 1997). These techniques can also provide information about the environment in which tasks are performed, such as tacit behaviors, social interactions, and physical demands, which are difficult to capture with other techniques (Kirwan and Ainsworth 1992). 

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. 

Such a task description invites task analysis, which would lead naturally to human reliability analysis (HRA). Indeed, perhaps the earliest work in this field applied HRA techniques to construct fault trees for aircraft structural inspection (Lock and Strutt 1985). The HRA tradition lists task steps, such as expanded versions of the generic functions above, lists possible errors for each step, then compiles performance shaping factors for each error. Such an approach was tried early in the FAA s human factors initiative (Drury et al. 1990) but was ultimately seen as difficult to use because of the sheer number of possible errors and PSFs. It is occasionally revised, such as in the current FRANCIE project (Haney 1999), using a much expanded framework that incorporates inspection as one of a number of possible maintenance tasks. Other attempts have been made to apply some of the richer human error models (e.g.. Reason 1990 Hollnagel 1997 Rouse 1985) to inspection activities (La-toreUa and Drury 1992 Prabhu and Drury 1992 Latorella and Prabhu 2000) to inspection tasks. These have given a broader understanding of the possible errors but have not helped better define the PoD curve needed to ensure continuing airworthiness of the civil air fleet. 

Bierbaum, C., Szabo, S., and Aldrich, T. (1989), Task Analysis of the UH-60 Mission and Decision Rules for Developing a UH-60 Workload Prediction Model. US Army Research Institute Aviation R D Activity, Fort Rucker, AL. 

Cognitive task analysis (CTA), 1024-1031 active participation in, 1027 examples of, 1032-1033 functional model derived from, 1027 scope of, 1025 stages in, 1025... 

Jiag, X., Master, R., Kelkar, K., Gramopadhye, A. K. (2002). Task analysis of shift activity in aviation maintenance environment Methods and findings. Human Factors and Aerospace Scfety, 2(1), 45-69. 

Rasmussen s cognitive task analysis Generic activities, knowledge states, and dependencies in task performance Knowledge requirements Task complexity... 

The technique for human error-rate prediction (THERP) [ Swain and Guttmann, 1980] is a widely applied human reliability method (Meister, 1984] used to predict human error rates (i.e., probabilities) and the consequences of human errors. The method relies on conducting a task analysis. Estimates of the likelihood of human errors and the likelihood that errors will be undetected are assigned to tasks from available human performance databases and expert judgments. The consequences of uncorrected errors are estimated from models of the system. An event tree is used to track and assign conditional probabilities of error throughout a sequence of activities. 

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