Network methods (internal)
Internal 2 credits Minimum spanning tree Shortest path Traversability Critical pathAS 91260, 2 credits — the one Level 2 statistics internal that is really discrete maths, graded on the SAME ladder as the calculus internals (apply methods / relational thinking / extended abstract thinking), not the "with justification" ladder the rest of this subject uses. Four techniques, and the assessed skill is choosing the right one for the question asked, then interpreting the answer in context.
1 Reading the notation
A borrowed ladder — this standard is graded like a maths standard, not like the rest of L2 statistics.📖 Terms the schedule grades you on
4 terms- Apply methods (Achieved)
- Select and use methods; demonstrate knowledge of network concepts and terms; communicate using appropriate representations.
- Named methods (note 4)
- Shortest paths, minimum spanning trees, critical path analysis (including float), network diagrams.
- Relational thinking (Merit)
- A logical sequence of steps, connecting concepts, or a model — AND relating findings to context.
- Extended abstract thinking (Excellence)
- A strategy, a chain of reasoning, or a generalisation — AND correct mathematical statements or insight.
2 Choosing the right technique
The question wording tells you which tool — this is most of the grade.| The question sounds like | Technique | Check on your answer |
|---|---|---|
| Connect every site as cheaply as possible | Minimum spanning tree | Exactly n − 1 edges, no cycles |
| Quickest / cheapest route from A to B | Shortest path (Dijkstra) | Labels only ever decrease |
| Travel every road exactly once | Traversability (Euler) | Count odd-degree nodes: 0 or 2 |
The commonest error is solving a shortest-path question with a spanning tree, or vice versa. Read what is being connected: every node, or two specific ones?
3 Critical path and float
The longest path sets the shortest possible finish — the counter-intuitive core of this technique. ✕Forward and backward passes swapped
Earliest start times take the LARGEST incoming value on a forward pass; latest start times take the SMALLEST outgoing value on a backward pass. Reversing either produces float values that look plausible but are wrong — always state which pass you are doing and why.4 Interpreting the answer
A correct network solution still needs a sentence converting it into the situation.What the context sentence needs
- The total cost, length, or time — with units.
- What action follows from the answer (which route, which activities to protect).
- For Excellence: a generalisation, or a strategy stated for an unfamiliar combined problem.
Practice
Recall it first, then use it — testing yourself builds the memory, where rereading the notes above only feels easier.
Recall and application shuffled together — you have to work out what each item wants before you can answer it, which is the part the exam actually tests. Both kinds feed the same spacing schedule, so anything you miss comes back sooner.
Say the answer out loud before flipping — that attempt is where the learning happens, even when you get it wrong.
Exam-style only. Instant feedback, shuffled each attempt, best score saved on this device.