In project planning, what tool is commonly used to illustrate the project schedule?

The choice of a PERT chart as a tool for illustrating the project schedule is well-founded due to its ability to visually represent the sequence of tasks and the time needed to complete each task within a project. PERT, which stands for Program Evaluation Review Technique, is specifically designed for project scheduling and focuses on the relationships among tasks, making it possible to identify dependencies and critical paths.

This tool effectively communicates how tasks are interrelated and helps project managers estimate the minimum time required to complete the entire project by analyzing the time it takes to complete individual tasks. It facilitates planning, scheduling, and coordinating project activities, which are vital components of successful project management.

The other choices, while useful in various aspects of project management, do not serve the specific purpose of illustrating project schedules. An affinity diagram is typically used for organizing ideas and identifying relationships between them. A risk matrix helps in analyzing and prioritizing risks associated with a project, and a fishbone diagram (or Ishikawa diagram) is primarily used for identifying potential causes of problems. None of these tools focus on scheduling tasks and their durations in a visual format, making the PERT chart the correct and most relevant choice for illustrating a project schedule.