Lec 14: Keystroke-Level Model (KLM)

Introduction

This tutorial provides a comprehensive overview of the Keystroke-Level Model (KLM), a fundamental concept in human-computer interaction. KLM helps in analyzing the efficiency of user interfaces by breaking down the actions a user takes to complete tasks. Understanding KLM is essential for designers and developers aiming to create user-friendly applications.

Step 1: Understanding the Keystroke-Level Model

• KLM quantifies the time it takes for users to perform tasks on a computer.

• It breaks down user actions into measurable units:

  • Keystrokes (K): Each key press, including function keys.
  • Pointing (P): Moving the mouse to click on items.
  • Homing (H): Returning hands to the keyboard from the mouse.
  • Mental preparation (M): Time spent thinking about the next action.

• The formula to calculate the total time (T) for a task is:

  T = (N * K) + (P * M) + H
  

Step 2: Identifying User Actions

• Determine the specific tasks users will perform. Common tasks include:
  • Opening applications
  • Navigating menus
  • Entering data
• Break these tasks down into individual actions, such as:
  • Typing commands
  • Clicking buttons
• Document each action to analyze time requirements accurately.

Step 3: Estimating Time for Each Action

• Use standard time estimates for each action:
  • Keystroke: 0.2 seconds
  • Pointing: 1.1 seconds (varies with distance)
  • Homing: 0.4 seconds
  • Mental preparation: 1.2 seconds
• Multiply the number of actions by the time estimates to calculate total task time.

Step 4: Applying KLM to Design Evaluation

• Use KLM to evaluate the design of user interfaces:
  • Create task scenarios that users are likely to encounter.
  • Estimate the total time for each task using the KLM formula.
  • Compare different interface designs based on total time estimates to identify which design is more efficient.

Step 5: Iterating on Design

• Gather feedback from real users to validate KLM estimates.
• Make iterative design changes based on user performance:
  • Simplify complex actions.
  • Reduce the number of required keystrokes or clicks.
• Reapply KLM to newly designed interfaces to measure improvements.

Conclusion

The Keystroke-Level Model is a valuable tool for understanding user interactions with technology. By breaking down tasks into measurable actions and estimating the time for each, designers can create more efficient user interfaces. Consider leveraging KLM in your design process to enhance usability and improve user experience. Next, explore how to integrate KLM findings into user testing and feedback loops for continual improvement.