Which delay matters?
A team is fitting a computer room. The PC order is two days late. Does the whole job slip? What if the wiring is two days late?
One delay changes nothing. The other moves the finish date. A diagram can tell you which is which.
By the end of this lesson
Note
I can read a precedence table and a PERT chart and find the critical path.
Key words
| Word | What it means |
|---|---|
| Precedence table | a table of tasks, their lengths and which tasks come first |
| Dependency | a task that must finish before another can start |
| PERT chart | a diagram of tasks joined by their dependencies |
| Critical path | the longest chain of tasks, which sets the project length |
| Float | the spare time a task can slip without delaying the project |
| Critical path analysis | finding the critical path and the float of each task |
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A precedence table lists what comes first
A precedence table has a row for each task. It gives the length of the task and which tasks must finish before it can start.
A task with nothing before it can start on day one. A task with several things before it must wait for the last of them.
Worked example: fitting a computer room
| Task | What it is | Days | Needs first |
|---|---|---|---|
| A | Order the PCs | 2 | Nothing |
| B | Prepare the room | 3 | Nothing |
| C | Install the PCs | 2 | A and B |
| D | Wire the room | 4 | B |
| E | Test everything | 1 | C and D |
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3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.