PERT/CPM notation: How is an event represented on a network diagram? In activity-on-arrow (AOA) or activity-on-node (AON) conventions, the event (milestone) is indicated by a number enclosed in which geometric shape?

Introduction / Context:
Network diagrams used in PERT/CPM display the logical sequence of project activities. An “event” or “milestone” denotes the instant when an activity begins or ends. Conventions were established to represent these clearly for calculations of earliest and latest event times.

Given Data / Assumptions:

• Classic activity-on-arrow (AOA) representation is considered.
• Events are zero-duration points defining the start or finish of activities.
• Standard drafting symbols are used to avoid ambiguity.

Concept / Approach:
In AOA, activities are arrows; nodes represent events. Historically, events are drawn as circles containing the event number. This aids clarity during forward (earliest event time) and backward (latest event time) passes. While AON uses boxes for activities, event circles remain standard for milestone depiction in AOA.

Step-by-Step Solution:
Establish that we are identifying the symbol for an event node.Recall the standard drafting practice: event number inside a circle.Select “a circle” to match conventional PERT/CPM notation.

Verification / Alternative check:
Common PERT/CPM references depict events as numbered circles (nodes) with connecting arrows as activities, confirming the chosen symbol.

Why Other Options Are Wrong:
Square, triangle, ellipse: Not the conventional AOA event symbol; could denote other diagrammatic elements but not the event node.All the above: Incorrect because a single standard shape is used.

Common Pitfalls:

• Mixing AON (boxes for activities) with AOA event symbols.
• Using inconsistent symbols that hinder team interpretation.

Final Answer:
a circle