Task analysis critical tasks

Behavioral observation and discussion Confined space Critical task analysis Critical task procedures Damage control Electrical safety Emergency preparedness Ergonomics Explosives... 

The development of the HRA event tree is one of the most critical parts of the quantification of human error probabilities. If the task analysis lists the possible human error events in the order of ihcir potential occurrence, the transfer of this information to the HRA event tree is fadlitutcd. Each potential eiTor and success is represented as a binary branch on the HRA event tiec. with subsequent errors and successes following directly from the immediately preceding ones. Cure should be taken not to omit the errors that are not included in the task analysis table but might affect the probabilities listed in the table. For example, administrative control errors that affect a task being performed may not appear in the task analysis table but must be included in the HRA event tree. 

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. 

By visual inspection of an OAET it is possible to identify the elements of a process control task which are critical in responding to an initiating event. An important issue in the construction of OAETs is the level of task breakdown. If the overall task is redescribed to very small subtasks it might be difficult to gain insights from the OAET because it Ccin become relatively unwieldy. Hierarchical Task Analysis provides a useful framework for the... 

The purpose of the Critical Task Identification and Screening analysis is to reduce the amoimt of analysis required by focusing on tasks that have a significant error potential. The screening process essentially asks the following questions ... 

PROBLEM DEFINITION. This is achieved through plant visits and discussions with risk analysts. In the usual application of THERP, the scenarios of interest are defined by the hardware orientated risk analyst, who would specify critical tasks (such as performing emergency actions) in scenarios such as major fires or gas releases. Thus, the analysis is usually driven by the needs of the hardware assessment to consider specific human errors in predefined, potentially high-risk scenarios. This is in contrast to the qualitative error prediction methodology described in Section 5.5, where all interactions by the operator with critical systems are considered from the point of view of their risk potential. 

Case study 5 provides an example from the offshore oil and gas production industry, and illustrates the fact that in solving a specific practical problem, a practitioner will utilize a wide variety of formal and informal methods. Table 7.1, which describes some of the methods used in the study, includes several techniques discussed in Chapter 4, including interviews, critical incident techniques, walk-throughs and task analysis. 

This section illustrates how the techniques described in Chapter 4 can be used to develop a procedure for the job of the top floor operator in the batch plant considered earlier. Two techniques are illustrated (i) a hierarchical task analysis (HTA) of the job, and (ii) a predictive human error analysis (PHEA) of the operations involved. HTA provides a description of how the job is actually done while PHEA identifies critical errors which can have an impact on the system in terms of safety or quality. The basic structure of the procedure is derived from the HTA which specifies in increasing detail the goals to be achieved. To emphasize critical task steps, various warnings and cautions can be issued based on the likely errors and recovery points generated by the PHEA. 

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. 

The results of CTA are usually cast in the form of graphical representations that incorporate the work demands and user strategies. For cognitive tasks that have been encountered in the past, operators may have developed well-established responses that may need some modifications but nevertheless provide a starting framework. For unfamiliar tasks that have not been encountered in the past or are beyond the design-basis of the system, operators are required to develop new methods or combine old methods in new ways. To illustrate how the results of CTA can be merged in a graphical form, two techniques are presented hierarchical task analysis and the critical decision method. 

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. 

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. 

Knowing the Objectives of Task Analysis Levels of Effort Criticality of Tasks... 

Attend at least two 8-hour safety training courses/seminars per year. (Examples include Modern Safety Management, Accident Investigation, Critical Task Identification and Analysis, Risk Assessment, Accredited Auditors.)... 

Based on the letrosynthetic analysis presented above, the first critical task on the way to testing the olefin metathesis-based strategy for the total synthesis of epothilone A (1) was the construction of the three key building blocks 61, 63, and 64. Focusing our attention first on the preparation of aldehyde 64, the Nicolaou group developed several approaches to this building block based on asymmetric synthesis with chiral auxiliaries one of these solutions is detailed in Scheme 19. 

The load model must represent real world conditions. Load modeling is a critical task in FEM because analysis using a formally correct, but inaccurate load model may lead to a result that will be accepted but mistaken. It may suggest development of poor quality even dangerous products. Complicated loads and... 

Describe each critical task in terms of all the subtasks (or steps) needed to carry it out. In general, the more complex the system the more detailed the task analysis becomes. Task analysis encompasses many techniques for describing how people interact with systems. Generally, a task analysis is a way of systematically describing human interaction with a system to understand how to match the demands of the system to human capabilities. No one task analysis method " can provide a complete understanding of... 

Task analyses can be very time-consuming, so the process requires competent oversight to ensure the effort is value adding, and as always, it is critical to focus the analysis on the end use of the data. A task analysis that has a broad scope and no specific focus may provide a comprehensive description of the system, but it may not be possible to complete with the available time and resource. Remember, one should always bear in mind that if a step or sequence of actions has not been considered, then it has certainly not been analysed. 

A Fault Tree Analysis (FTA), which can take the failure of a critical task and identify all subtasks and other causes contributing to that failure condition. 

According to this rating, a screening of the human performance is performed. Moreover, since a nominal task analysis has been performed to analyse all tasks in sequence, probabilities for human errors that can lead to deviations from the required sequence can be estimated. Critical PSFs have been also identified and their impact to the human error probability is evaluated with the FPE. Additionally, critical operating and recovery points needing improvements are identified. The imp act o f the se improvements to the overall hmnan performance is depicted through the use of the FPE tool. This whole process is explained with the use of a specific example. 

The Task Analysis scope is to provide a common means of communication between the technical persoimel involved in the interviews, the human factors experts and the VR experts to reach a common understanding of the task to be reproduced in the experiments, its main objective, challenges and criticalities (Leva, 2009). The Nominal Task Analysis has been prepared... 

The Nominal Task Analysis was linked to the risk assessment analysis for the critical scenarios identified as relevant to the case study while the hnk between the safety barriers and the activities identified in the task has been also estabhshed. Additionally the task analysis has been used to describe in detail the actions connected with a specific safety barrier related to a relevant accidental scenario and the mode the latter can be represented in the VR experiments. 

Deviations are in fact analysed for all the activities identified as critical (as being part of a safety barrier) according to the bow-tie analysis of the accidental scenarios. Every step considered to be critical and therefore represented more in depth in the detail task analysis is associated with the Ust of relevant PSF affecting it for the scope of experiment design. 

The Human Factors analysts needed an approach and a tool to help them in providing a template for the interview process of a Task analysis with the ability to structure the interview phase in order to highlight and examine the deviations from standard practice. These deviations are fundamental to understanding what can and does go wrong in the field and should be an integral part of any safety critical task representation. A graphical representation of the procedure map linked to the template including ... 

The effectiveness and validation of the representation method is not the only aspect to be considered for evaluating task analysis tools. Other critical aspects have to be considered ... 

Task criticalities evaluation connection between the phase of the task criticalities evaluation and the methods used for the task analysis itself (likely chance data collection phase is missing much of the information useful in the evaluation phase). 

The task analysis provides a structured description of the activities that permits a high-profiling of the task, the context ofworkandthe users needs. However, task analysis is more focused on what the operators are expected to do than on how they actually perform their activities from their own perspective. Another method, based on user scenarios, seems to be more suitable to examine user activities from the visual perspective (e.g. location, gaze direction, affordances and constraints on movement) and generate functional and usability specifications for virtual environments (VE). The critical hnk for this information is the fact that for each node of the task model (especially critical decision-points), the important performance shaping factors and tools to be used are recorded. They are... 

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