Introduction_to_Human_Factors_and_Ergonomics_----__Pg_70--74_

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.