Critical path analysis
| English | Chinese | Pinyin |
|---|---|---|
| critical path analysis | 关键路径分析 | guān jiàn lù jìng fēn xī |
| network diagram | 网络图 | wǎng luò tú |
| activity | 活动 | huó dòng |
| duration | 工期 | gōng qī |
| nodes | 节点 | jié diǎn |
| critical path | 关键路径 | guān jiàn lù jìng |
| float | 浮动时间 | fú dòng shí jiān |
The schedule that can't slip
- A big project — a building, a product launch — has dozens of tasks, some at once, some in sequence.
- Critical path analysis 关键路径分析 (CPA) finds the fastest way through and the tasks that must not be late.
A diagram of activities, durations and dependencies used in CPA is a ______ diagram.
The network diagram is the basis of critical path analysis.
Networks of activities
- A network diagram 网络图 shows each activity 活动, its duration 工期, and what must finish before it can start.
- Nodes 节点 mark events (start/finish points); arrows are the activities.
The critical path 关键路径 is the longest route through the network — it sets the minimum project time.
Critical path analysis
CPA finds the sequence of tasks that decides the shortest time a project can take.
The critical path is the:
The longest route determines the minimum completion time.
Float is:
Float is slack time on non-critical activities.
The critical path and float 浮动时间
- The critical path is the sequence of activities with no spare time — any delay delays the whole project.
- Float is the spare time a non-critical activity has before it would hold things up.
Worked example. If path B-D-E takes 4 + 5 + 2 = 11 days and every other route is shorter, then 11 days is the minimum project time, and B, D and E are critical — no float.
A critical path network with the critical path of zero-float activities highlighted
Find the critical path
Drag the durations — the network rolls forward and back, the floats update, and the critical path jumps to whichever route is longest.
A critical path runs through activities of 3, 5 and 4 days. What is the minimum project duration (days)?
3 + 5 + 4 = 12 days along the critical path.
A delay to an activity on the critical path delays the whole project.
Critical activities have no float to absorb a delay.
Why CPA helps
- It reveals the shortest possible completion time and which tasks to watch.
- It helps schedule resources and run activities in parallel to save time.
A delay on the critical path delays everything. Non-critical tasks have float to absorb slips; critical ones do not. Managers must protect the critical path above all.
You've got it
- a network diagram shows activities, durations and dependencies
- the critical path is the longest route — it sets the minimum project time
- float is spare time on non-critical tasks; a delay on the critical path delays the project