Project Planning
Project planning defines the steps needed to deliver the project, estimates the effort for each step, sequences the work, and assigns resources. The plan is the baseline against which progress is measured.
Work Breakdown Structure (WBS)
A WBS decomposes the total work into manageable work packages. Rules:
- Each level is a complete but smaller view of the level above.
- Each work package should produce a tangible deliverable.
- A work package should take 8 to 80 hours (the "8/80 rule").
- Leaves of the WBS are the tasks you schedule.
Effort Estimation
Common techniques:
- Expert judgement — ask experienced team members.
- Analogous — compare to similar past projects.
- Parametric (COCOMO, function points) — formula based on size.
- Three-point (PERT):
Expected = (Optimistic + 4 · Most Likely + Pessimistic) / 6. - Bottom-up — estimate each WBS leaf and roll up.
Gantt Chart
A Gantt chart is a horizontal bar chart where each bar is a task, its length shows duration, and position along the time axis shows start and end dates. Vertical dependencies can be drawn between bars. Gantt charts are simple and visual but do not highlight the critical path.
Network Diagrams — PERT and CPM
Both PERT and CPM represent tasks as nodes (or arrows) with dependency arrows between them.
- CPM (Critical Path Method) uses one deterministic duration per task.
- PERT (Program Evaluation and Review Technique) uses the three-point estimate above.
Critical Path
The critical path is the longest path from start to end. Its length equals the shortest possible project duration. Any delay on a critical task delays the whole project. Compute by a forward pass (earliest start/finish) and backward pass (latest start/finish); tasks with zero slack are critical.
Float / Slack
Slack is the amount of time a task can slip without delaying the project. Total slack = LF - EF (latest finish minus earliest finish). Non-critical tasks have positive slack.
Resource Leveling
After scheduling, check if any resource is over-allocated. Resource leveling shifts non-critical tasks within their slack to smooth the resource demand. If leveling cannot fit, the project deadline must extend or more resources added.
Project Monitoring
Once execution starts, track progress through status reports, earned value analysis, and milestone reviews. Earned value (EV) compares planned value, earned value, and actual cost to detect schedule and cost variance early.
Summary
Planning decomposes the project into a WBS, estimates effort, sequences tasks on a Gantt or network diagram, identifies the critical path, and levels resources. The plan is continuously updated as reality unfolds.
Important Questions
- What is a Work Breakdown Structure? Explain the 8/80 rule.
- List and describe effort-estimation techniques.
- Compute an expected PERT duration for O=4, M=6, P=14.
- What is a Gantt chart? List its strengths and weaknesses.
- Differentiate PERT and CPM.
- Define critical path. How is it computed?
- What is slack? Why are critical tasks monitored more closely?
- Explain resource leveling with an example.