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Task Analysis in Human Factors and Ergonomics

Importance of Task Analysis

  • Essential for applying ergonomic principles in system design.

  • Involves gathering data on task performance via observation, recording interactions, and user debriefs.

  • Fundamental for risk assessment techniques.

Definition and Purpose

  • Defined by Snyder (1991) as an ordered sequence of tasks and subtasks identifying:

    • Performer/user

    • Actions/activities/operations

    • Environment

    • Starting state and goal state

    • Requirements (hardware, software, information).

  • Drives human-centered design by providing system-specific context for ergonomics.

General Procedure for Task Analysis (Rasmussen 1983)

  1. Identify a prototypical task by collecting expert user descriptions.

  2. Identify all processes involved in the task.

  3. Analyze action options and selection criteria.

  4. Generate a task specification:

    • Identify participants

    • Define subcomponents of the activity

    • Detail participant roles and information requirements

    • Assess information sources and exchanges

    • Propose improvements.

Outcomes of Task Analysis

  • Provides:

    1. Required behaviors for task completion.

    2. Descriptions of system states during task execution.

    3. Mapping of behaviors onto system states, identifying potential issues in design.

Example Context

  • Discusses postural issues faced by operators leading to musculoskeletal problems, highlighting the need for adequate training, resources, and feedback mechanisms in improving ergonomics.

Uses of Task Analysis

  • Used for:

    1. Evaluating human–machine interfaces.

    2. Identifying operator skills required for system use.

    3. Designing training materials and operating instructions.

    4. Identifying critical task elements for reliability evaluations.

Hierarchical Decomposition of a Job (Table 1.3)

  • Breakdown of tasks from job title to specific operations to document processes effectively.

Questions for System Designers (Table 1.4)

  • Key questions:

    • How to invoke operator task behaviors?

    • System responses to task execution?

Historical Context of Task Analysis

  • Developed by Professor J. Annett in the 1970s, rooted in time and motion studies by Gilbreths and principles from scientific management.

  • Emphasizes the need for detailed task analysis to maintain efficiency and safety.

Ensuring Effective Task Analysis

  • Establish clear task boundaries (start and end points).

  • Maintain hierarchical understanding without overcomplicating early stages.

  • Focus on high-level tasks before diving into detailed analysis.

Basic Task Analysis Example: Making a Sandwich (HFE Workshop 1.2)

  • High-level overview of making a cheese sandwich with subtasks and operations defined clearly.

  • Visual representation of task flow and decision-making process outlined in figures.

Status of Risk Assessment and Design Tools

  • Ergonomics tools are expanding in functionality for assessing risks and aiding design processes.

  • Validity and reliability are crucial for effective tools:

    1. Validity: Measures what it is intended to measure (content, construct, criterion).

    2. Reliability: Consistency of results under the same conditions (test-retest, inter-tester).

    3. Sensitivity: Ability to detect important differences.

    4. Diagnosticity: Detailed enough to reveal differences in situations.

Task Flow Diagram Description

  • Represents high-level task description with decision-making points.

  • Encourages breaking down subtasks for further analysis as necessary.