Project planning - Planning and managing schedule

Learning Outcomes

After reading this article, you will be able to describe key schedule planning and management activities for projects, including defining and sequencing activities, estimating durations, constructing and analyzing the project schedule, using the critical path method, applying float, and managing schedule constraints. You will also understand PMP-relevant methods for compressing schedules and controlling project timelines.

PMP Syllabus

For PMP, you are required to understand how to plan and manage a project schedule in both predictive and adaptive environments. Focus your revision on:

• Identifying and defining project activities using the work breakdown structure (WBS) or backlog.
• Determining dependencies and sequencing project activities (mandatory, discretionary, external, internal).
• Estimating activity durations using different methods (analogous, parametric, three-point/PERT, relative).
• Developing the project schedule and understanding schedule models, network diagrams, and presentation formats (Gantt, milestone charts).
• Applying the critical path method to identify project constraints.
• Calculating and interpreting float (slack) and using it in resource optimization.
• Implementing schedule compression techniques such as crashing and fast-tracking.
• Monitoring schedule progress, tracking variances, and controlling changes to the schedule.
• Applying these methods in both predictive and adaptive (agile) environments.
• Using velocity and cumulative flow diagrams for schedule tracking in agile projects.

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. In project scheduling, which method identifies the sequence of activities that determine the shortest possible project duration?
   1. Rolling wave planning
   2. Critical path method
   3. Resource histogram
   4. S-curve
2. In the precedence diagramming method, which dependency type requires one activity to finish before the next can start?
   1. Start-to-start
   2. Finish-to-finish
   3. Finish-to-start
   4. Start-to-finish
3. Which estimating technique uses historical data from similar past activities to estimate activity durations?
   1. Three-point estimating
   2. Analogous estimating
   3. Parametric estimating
   4. Monte Carlo analysis
4. What does the ‘float’ (slack) of an activity represent in a project schedule?
   1. The number of resources needed
   2. The time an activity can be delayed without affecting the project end date
   3. The cost over baseline
   4. The quality margin

Introduction

Planning and managing the schedule is a core responsibility of the project manager throughout the project life cycle. Creating a structured schedule ensures all project work is clearly defined, sequenced, estimated, and tracked. This enables timely delivery of project objectives and provides the basis for measuring, forecasting, and controlling project performance. Schedule planning must account for limitations, dependencies, and risks and be tailored for predictive, agile, or hybrid approaches.

Defining Activities

The first step in schedule planning is to break down the project scope into manageable activities. In predictive projects, this is done by decomposing deliverables in the work breakdown structure (WBS) into activities.

Key Term: Activity A specific, scheduled piece of work required to complete a work package or user story.

In agile projects, activities are derived from the prioritized product backlog, with features decomposed into user stories and tasks for each cycle.

Sequencing Activities

Once activities are defined, the project manager determines their logical sequence. Dependencies between activities determine which must precede others.

Key Term: Dependency The relationship between two activities, dictating the order in which they must be performed.

Key Term: Mandatory Dependency A relationship essential to the nature of the work (hard logic, e.g., concrete must cure before painting).

Key Term: Discretionary Dependency Based on best practice, preference, or convenience (soft logic, e.g., painting before installing carpet).

Key Term: External Dependency A relationship between a project activity and an activity outside the project’s control (e.g., waiting for regulatory approval).

Key Term: Internal Dependency A relationship between two activities within the project team's control.

The precedence diagramming method (PDM) is commonly used, where activities are represented as nodes and dependencies are shown as arrows. The most common type is Finish-to-Start (FS).

Estimating Activity Durations

After sequencing, each activity’s duration is estimated. Several methods can be employed:

Key Term: Analogous Estimating Estimating activity durations using historical data from similar past activities.

Key Term: Parametric Estimating Applying a mathematical model to scale duration estimates based on quantities (e.g., installation time per meter).

Key Term: Three-Point Estimating Calculating duration based on optimistic, pessimistic, and most likely estimates (e.g., PERT formula).

Key Term: Relative Estimating Comparing activity size and complexity to similar activities or using affinity methods (common in agile).

Schedule Development

With activities defined, sequenced, and estimated, the schedule model can be constructed. Tools like Gantt charts or milestone charts may be used to visualize the plan. The network diagram forms the basis for calculating the critical path and float.

Key Term: Critical Path The sequence of activities with zero float that determines the minimum completion time for the project; delay of any activity on the critical path will delay the whole project.

Calculating Float (Slack)

Key Term: Float (Slack) The amount of time an activity can be delayed without delaying the project end date or a successor activity.

Float can be total (without impacting the project end date) or free (without impacting successor activities). The critical path always has zero float.

Schedule Compression and Resource Optimization

If the proposed schedule does not meet the required completion date, the manager can apply schedule compression:

• Crashing: Adding resources to shorten duration (higher cost, may increase risk).
• Fast-tracking: Performing activities in parallel that were originally sequential (increases risk).

Float is also used for resource smoothing (reshuffling non-critical activities to resolve allocation conflicts without changing the end date) and resource leveling (delaying activities as needed when resources are over-allocated, which may extend the schedule).

Schedule Control and Monitoring

Ongoing measurement and control are required to ensure work proceeds as planned and schedule baselines are maintained:

• Monitor actual progress against planned dates and milestones.
• Identify and analyze variances.
• Implement corrective or preventive actions if activities are delayed.
• Use Earned Value Management (EVM) and performance indexes (SPI) in predictive projects.

Adaptive (Agile) Scheduling Practices

In agile, work is delivered in fixed time-boxed cycles. The team’s velocity (average work completed per cycle) provides a basis for forecasting completion. The backlog is regularly refined to ensure enough ready work is always available.

Cumulative flow diagrams and burndown charts give rapid feedback on flow and lead time, enabling quick responses to bottlenecks and ensuring continuous delivery.

Worked Example 1.1

A project network diagram contains five activities in a finish-to-start sequence as follows:

• A (5 days), B (4 days), C (6 days), D (3 days), E (2 days).
  Assume no other paths.

What is the project’s critical path and total duration? If Activity C is delayed by 2 days, what is the impact on project completion?

Answer:
The critical path is A–B–C–D–E: 5+4+6+3+2 = 20 days.
If Activity C is delayed by 2 days, the critical path becomes 22 days. The project end date is delayed by 2 days.

Worked Example 1.2

In an agile project, the team’s velocity is 25 story points per sprint. The backlog contains 150 story points. How many sprints are needed to complete the backlog, assuming velocity remains stable and no new work is added?

Answer: Total sprints = 150 / 25 = 6 sprints.

Exam Warning

Activities not on the critical path may still delay the project if float is consumed by changes. On the exam, always double-check if more than one path may become critical if activities are delayed.

Revision Tip

Practice drawing a simple network diagram and calculating the critical path and float manually. This is commonly tested and helps build confidence for schedule calculations.

Summary

Planning and managing the project schedule involves defining, sequencing, and estimating activities; building a schedule model; calculating the critical path and float; applying schedule compression or resource optimization as needed; and monitoring and controlling the schedule baseline. Both predictive and adaptive (agile) approaches require regular tracking, stakeholder communication, and prompt responses to variances to ensure on-time delivery.

Key Point Checklist

This article has covered the following key knowledge points:

• The schedule establishes a structured timeline for project activities and deliverables.
• Activity definition and sequencing use the WBS or backlog and dependency analysis.
• Estimate durations using appropriate methods: analogous, parametric, three-point, and relative estimating.
• The network diagram, critical path, and float identify schedule constraints and flexibility.
• Schedule compression (crashing, fast-tracking) and resource optimization help address constraints or conflicts.
• In agile, forecast completion with team velocity and adjust the plan using flow diagrams and regular reviews.
• Schedule monitoring and control require tracking progress, managing baseline changes, and early corrective actions.

Key Terms and Concepts

• Activity
• Dependency
• Mandatory Dependency
• Discretionary Dependency
• External Dependency
• Internal Dependency
• Analogous Estimating
• Parametric Estimating
• Three-Point Estimating
• Relative Estimating
• Critical Path
• Float (Slack)