Project Scheduling and Critical Path Analysis Cheat Sheet

Updated 2026-05-28

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Project scheduling is the process of defining project activities, sequencing them logically, estimating durations, and developing a timeline that predicts when work will be performed and completed. It sits at the heart of project management, driving resource allocation, cost control, and stakeholder communication. The Critical Path Method (CPM) revolutionized this field by identifying the longest sequence of dependent tasks that determines the minimum project duration—any delay on this path delays the entire project. What makes modern scheduling powerful is not just finding the critical path, but understanding float, dependencies, and variance tracking to dynamically adapt as conditions change, turning static plans into living, decision-ready models.

What This Cheat Sheet Covers

This topic spans 25 focused tables and 147 indexed concepts, 129 flashcards. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.

Table 1: Network Diagram TypesTable 2: Dependency TypesTable 3: Critical Path CalculationsTable 4: Float and Slack TypesTable 5: Duration Estimation MethodsTable 6: Schedule Compression TechniquesTable 7: Gantt Chart ElementsTable 8: Earned Value Schedule MetricsTable 9: Schedule Forecasting MetricsTable 10: Resource Optimization TechniquesTable 11: Constraint TypesTable 12: Critical Chain Project ManagementTable 13: Activity TypesTable 14: Schedule Baseline and ControlTable 15: Progress Update MethodsTable 16: Schedule Risk AnalysisTable 17: Work Breakdown and Activity DefinitionTable 18: Calendar and Time ConceptsTable 19: Advanced Scheduling TechniquesTable 20: Schedule Quality MetricsTable 21: Schedule Reserve and BuffersTable 22: Schedule Software and ToolsTable 23: Specialized Planning ApproachesTable 24: Duration vs. Effort vs. Elapsed TimeTable 25: Linear and Location-Based Scheduling

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Table 1: Network Diagram Types

The type of network diagram you choose determines how activities are represented and what kinds of logic are supported. PDM/AON is the dominant modern format; AOA and GERT remain useful for specialized cases.

Method	Example	Description
Precedence Diagramming Method (PDM)	Boxes `A` `→` `B` `→` `C` with arrows between nodes	• Activities shown as nodes (boxes), arrows show dependencies • also called Activity-on-Node (AON) • supports all four dependency types.
Activity-on-Node (AON)	Node contains: `Task A` `ES=0, EF=5` `LS=0, LF=5`	• Most common modern format where nodes represent activities and arrows represent logical relationships • simpler than AOA, no dummy activities needed.
PERT Chart	Three boxes: `Design`, `Build`, `Test` with probabilistic durations	• Network diagram that uses three-point estimates (optimistic, most likely, pessimistic) for each activity • emphasizes uncertainty and probability.
Critical Path Network	Path `A→B→D→F` highlighted in red with zero float	• Network diagram with the longest dependency path visually distinguished • shows which activities cannot be delayed without impacting project completion.
Activity-on-Arrow (AOA)	Node `1` `→` (Activity A) `→` Node `2`	• Activities shown as arrows, nodes represent events/milestones • only supports finish-to-start dependencies • requires dummy activities for complex logic.
GERT (Graphical Evaluation and Review Technique)	Task A → (70% success → B) or (30% loop back → A)	• Extends CPM/PERT with probabilistic branching, loops, and conditional paths • supports AND/OR/XOR input logic and repeated activities • rarely used in practice; best for complex stochastic processes.

Table 2: Dependency Types

Understanding all four dependency types—and when to add leads or lags—is essential for building a realistic network. The vast majority of real-world dependencies are Finish-to-Start; the others model concurrent or constrained relationships.

Type	Example	Description
Finish-to-Start (FS)	Task A finishes Dec 5 `→` Task B starts Dec 6	• Most common dependency • successor cannot start until predecessor finishes • represents sequential work.

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Table 3: Critical Path Calculations

The CPM forward and backward pass produces Early Start, Early Finish, Late Start, and Late Finish for every activity. Activities where ES = LS (or EF = LF) sit on the critical path with zero total float.

Term	Example	Description
Early Start (ES)	Activity C: ES = 10 days	• Earliest an activity can begin • calculated in forward pass • equals the latest EF of all predecessors.

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Table 4: Float and Slack Types

Float (also called slack) measures scheduling flexibility. Total float belongs to the path, not the individual activity—consuming it on one task removes it from all others on the same path.

Type	Example	Description
Total Float (TF)	$\text{TF} = \text{LS} - \text{ES} = 13 - 10 = 3$ or TF = LF - EF	• Maximum time an activity can be delayed without delaying project completion • critical path activities have TF = 0.

The rest of this section is part of the full cheat sheet

Table 1: Network Diagram Types

Method	Example	Description
Precedence Diagramming Method (PDM)	Boxes `A` `→` `B` `→` `C` with arrows between nodes	• Activities shown as nodes (boxes), arrows show dependencies • also called Activity-on-Node (AON) • supports all four dependency types.
Activity-on-Node (AON)	Node contains: `Task A` `ES=0, EF=5` `LS=0, LF=5`	• Most common modern format where nodes represent activities and arrows represent logical relationships • simpler than AOA, no dummy activities needed.
PERT Chart	Three boxes: `Design`, `Build`, `Test` with probabilistic durations	• Network diagram that uses three-point estimates (optimistic, most likely, pessimistic) for each activity • emphasizes uncertainty and probability.
Critical Path Network	Path `A→B→D→F` highlighted in red with zero float	• Network diagram with the longest dependency path visually distinguished • shows which activities cannot be delayed without impacting project completion.
Activity-on-Arrow (AOA)	Node `1` `→` (Activity A) `→` Node `2`	• Activities shown as arrows, nodes represent events/milestones • only supports finish-to-start dependencies • requires dummy activities for complex logic.
GERT (Graphical Evaluation and Review Technique)	Task A → (70% success → B) or (30% loop back → A)	• Extends CPM/PERT with probabilistic branching, loops, and conditional paths • supports AND/OR/XOR input logic and repeated activities • rarely used in practice; best for complex stochastic processes.

Table 2: Dependency Types

Type	Example	Description
Finish-to-Start (FS)	Task A finishes Dec 5 `→` Task B starts Dec 6	• Most common dependency • successor cannot start until predecessor finishes • represents sequential work.

Table 3: Critical Path Calculations

Term	Example	Description
Early Start (ES)	Activity C: ES = 10 days	• Earliest an activity can begin • calculated in forward pass • equals the latest EF of all predecessors.

Table 4: Float and Slack Types

Float (also called slack) measures scheduling flexibility. Total float belongs to the path, not the individual activity—consuming it on one task removes it from all others on the same path.

Type	Example	Description
Total Float (TF)	$\text{TF} = \text{LS} - \text{ES} = 13 - 10 = 3$ or TF = LF - EF	• Maximum time an activity can be delayed without delaying project completion • critical path activities have TF = 0.