Worked example · Design Technology · Year 11
DCF: Producing → Sourcing, searching and planning digital content
A secure Year 11 response, annotated against the success criteria. The start and finish weeks and the chart are the only correct ones, so you can mark from them. Key answers: the plan finishes in week 13 with 1 week of contingency; the critical path is A, B, E, F, G, H, I; float is C 3, D 2, J 7 weeks; the laser cutter problem does not move the finish, the supplier delay moves it to week 14.
2 + 2 + 1 + 1 + 3 + 1 + 2 + 1 + 2 + 3 = 18 weeks of work, but only 14 weeks until hand-in. Doing one task at a time she would miss the deadline by 4 weeks. So Elin has to run tasks side by side wherever the "must wait for" column allows it — and she needs to know which tasks those are.
Uses the total to show why overlapping tasks is necessary, not just nice to have. Sets up criterion 1.
| Task | Weeks | Waits for | Start | Finish | Reasoning |
|---|---|---|---|---|---|
| A | 2 | — | 1 | 2 | Given. |
| B | 2 | A | 3 | 4 | A finishes in week 2. |
| C | 1 | A | 3 | 3 | Runs alongside B. |
| D | 1 | B and C | 5 | 5 | C is done in week 3 but B not until week 4, so the later one decides. |
| E | 3 | B | 5 | 7 | Needs the timber from the delivery. |
| F | 1 | D and E | 8 | 8 | D is done in week 5, E in week 7: waits for E. |
| G | 2 | F | 9 | 10 | |
| H | 1 | G | 11 | 11 | |
| I | 2 | H | 12 | 13 | |
| J | 3 | C | 4 | 6 | Can start as soon as the model exists. |
Every date is right, and the two tasks with two dependencies (D and F) are handled by taking the later finish. Evidences criterion 1.
Every bar starts and ends on the right week, the critical path is picked out, float is drawn as a dashed box so it can be seen, and the key works in black and white because the three styles differ in shading and outline, not only colour. Evidences criteria 2 and 3.
(a) The project finishes at the end of week 13, when the evaluation (I) is done. Hand-in is the end of week 14, so there is 1 week of contingency.
(b) A → B → E → F → G → H → I. 2 + 2 + 3 + 1 + 2 + 1 + 2 = 13 weeks, which is exactly the finish week, so there is no slack anywhere along it.
| Task | Float | How I worked it out |
|---|---|---|
| C | 3 weeks | D must be done by week 7 so F can start in week 8, so D can start as late as week 7 and C can finish as late as week 6. Earliest finish week 3, latest week 6. |
| D | 2 weeks | Earliest week 5, latest week 7, because F does not start until week 8 anyway (it is waiting for E). |
| J | 7 weeks | Nothing waits for J, so it only has to be done by week 13. Earliest finish week 6, latest week 13. |
Finds the critical path by its length matching the finish week, and works out each float from the task that waits for it, not by eye. Evidences criterion 3.
(a) Task D, the laser cutting. It was planned for week 5, which is now out, and week 6 is out too, so D moves to week 7. D has 2 weeks of float, and moving from week 5 to week 7 uses exactly those 2 weeks. F still starts in week 8, so the finish stays at week 13. The catch: D now has no float left, so it has joined the critical path. If anything else delays it, the project slips.
(b) B now takes weeks 3 to 5. E moves to weeks 6 to 8, F to week 9, G to weeks 10 to 11, H to week 12, and I to weeks 13 to 14. The project finishes at the end of week 14, on the hand-in day, with no contingency at all. One week here matters more than two weeks in (a) because B is on the critical path, with zero float, so every week it slips pushes every task after it. D's two weeks were soaked up by float.
Traces each delay through the dependencies, uses float to explain why one delay costs nothing and the other costs the whole contingency, and notices that the laser cutter problem quietly makes D critical. Evidences criterion 4.
(a) Change 1: use timber from the school's stock for the base, so E waits only for A instead of for the delivery. Then E runs in weeks 3 to 5 alongside the delivery. B still ends in week 5, so D is in week 6, F in week 7 (both D and E are done by week 6), G in weeks 8 to 9, H in week 10 and I in weeks 11 to 12. New finish: week 12, which is 2 weeks of contingency — better than the original plan.
Change 2: place the order in week 2, as soon as the CAD model fixes the sizes of the acrylic and the base, instead of waiting for the finished drawings. B then runs weeks 2 to 4 even with a 3-week delivery, and the original week-13 finish comes back. The risk is ordering the wrong size if the design changes in week 2, so I would only order once the key dimensions are signed off.
(b) Elin should not guess a lead time. She could check the delivery time stated on the supplier's own website for each item, and then email the supplier to confirm it in writing before ordering, since stock levels change. The DT technician will know how long the same supplier took on past orders, which is real evidence rather than an advertised figure. To reduce the risk she could order the standard parts (the LED kit) in week 1 because they do not depend on the design, check what the school already has in stock, and note a second supplier in case the first one is late.
Two workable changes with the dependency change stated exactly and one fully re-dated; the second admits its own risk. The sourcing answer ranks sources by reliability (written confirmation and past orders above an advertised figure). Evidences criterion 5.