Lab 16 — Schedule Compression Trade-offs¶
At a glance
- Modules: 06 — Schedule Management
- Level: Advanced
- Estimated time: 105–120 minutes
- Deliverable: A crash table, a re-analysis after each compression, and a recommendation with its price
- Template: none — the crash table is yours to design; the schedule worksheets cover the forward and backward pass
- Answer key: Advanced labs answer key — includes the full compression analysis
Learning objectives¶
By the end of this lab you should be able to:
- Identify which activities can be compressed to shorten a project, and which cannot.
- Recalculate the critical path after each compression rather than assuming it stays the same.
- Compare crashing, fast-tracking, and scope reduction on cost and on risk.
- Cost a schedule compression decision per day saved, and recommend one with its consequences stated.
Scenario¶
This lab uses the Mobile Banking Application from Lab 04. The programme board has moved the launch because of a regulatory reporting deadline: the release must be ready two working days earlier than the current plan.
The plan:
| # | Activity | Duration (days) | Predecessors | Can it be compressed? |
|---|---|---|---|---|
| A | Design and authentication flow | 3 | — | No — already minimal; the whole team is needed |
| X | Payment API integration | 8 | A | Yes — to 6 days for PKR 90,000, by borrowing a specialist |
| Y | Fraud rules configuration | 6 | A | Yes — to 4 days for PKR 120,000, by borrowing a specialist |
| Z | Mobile UI build | 7 | A | Yes — to 5 days for PKR 80,000, by borrowing a designer |
| I | Integration testing | 4 | X, Y, Z | No — testing duration cannot be reduced without reducing coverage |
| R | Release preparation | 2 | I | No — the security specialist's sign-off is a fixed two-day process |
The borrowed resources come from another programme. If you borrow a specialist for a period, the other programme's delivery slips by the same period; that cost is not in the figures above and is a political consequence you must state.
Additional options on the table:
| Option | Description |
|---|---|
| Fast-track | Start integration testing on the payment path before X is fully complete, at rework risk |
| Descore | Remove the "card blocking" screen from the release, reducing Z by 2 days at no additional cost |
| Add a second test path | Run payment-path testing and UI testing in parallel, requiring two test environments (not currently available) |
| Move the date | Report to the board that two days is not achievable without a consequence |
Facts:
- The security specialist's process is fixed at two days and cannot be compressed at any price.
- X, Y, and Z can each be compressed by at most two days.
- Fast-tracking X and I saves at most two days, and the programme's quality lead estimates a 40% chance of one extra day of rework in integration testing.
- No additional budget has been approved for compression.
Your role¶
You are the project manager. You must bring the board a recommendation with its price, not a request for a decision without data.
Project information and assumptions¶
The scenario is part of the example-project library — read the full description there if you want the wider context.
- Express all calculations in days and PKR, and show your working at each step.
- Recalculate the critical path after every change you consider. The path can move, and a compression applied to a non-critical activity saves nothing.
- Assume the other programme's slip is a real cost even though it does not appear in the table.
Tasks¶
Task 1 — Establish the baseline¶
- Complete a forward pass and state the project duration.
- Identify the critical path and the total float of every non-critical activity.
- State which activities are candidates for compression, and which are not — with the reason.
Task 2 — Cost the compression per day¶
For X, Y, and Z, calculate the cost per day saved by compressing each. Show the arithmetic in a table:
| Activity | Normal duration | Compressed duration | Days saved | Cost | Cost per day |
|---|---|---|---|---|---|
Then answer: two of these three activities have positive float. What does that mean for the cost per day saved of the project?
Task 3 — Compress one day¶
Restate the schedule with the compressed activity. Then:
- Recalculate the forward pass and the duration.
- State the new critical path, and whether a second path has appeared.
- State the cost of the first day saved.
Task 4 — Compress the second day¶
Compress again — but first answer: which activity must now be compressed, and why is it not simply the next cheapest one?
Then complete the compression, recalculate, and state the cost of the second day saved.
Task 5 — Total the cost¶
- State the total cost of saving two days by crashing.
- State the marginal cost of the second day compared with the first, and explain the pattern.
- State the consequence for the other programme in one sentence.
Task 6 — Evaluate the alternatives¶
For each of the three alternatives — fast-tracking, descoping card blocking, and reporting that the date cannot move — record:
| Option | Days saved | Direct cost | Risk created | Consequence for scope or quality |
|---|---|---|---|---|
For fast-tracking, include the expected cost of the rework risk using the 40% probability given.
Task 7 — Recommend¶
Write a recommendation of no more than 250 words to the programme board containing:
- The option you recommend, and the days it delivers.
- Its cost, including the cost that does not appear on the table.
- Its risk, stated in one sentence with the probability where one is known.
- What you would do if the board rejected your recommendation.
- One thing you will not do, and why.
Then state the single piece of information that would most change your recommendation.
Deliverable¶
- The baseline: duration, critical path, float table, compressible activities.
- The cost-per-day table with arithmetic.
- Two recalculated compressions with the new critical path each time.
- The total cost, the marginal cost pattern, and the other programme's consequence.
- The alternatives table with the expected rework cost included.
- A recommendation of no more than 250 words.
- The information that would change your mind.
Hints and guidance¶
- Compression only works on the critical path. Z has float, so compressing Z before X is compressed buys nothing at all.
- After the first compression the critical path can move. That is the entire point of Task 4: the second day is not simply the next cheapest item on the original list.
- Cost per day is a marginal concept. The second day is usually more expensive than the first, and that rise is the information the board needs.
- Free compression is never free. Descoping is cheap in cash and expensive in product.
- State the risk, not just the cost. A 40% chance of a day of rework is a number the board can reason about; "there is some risk" is not.
Self-check criteria¶
| Check | How to verify it |
|---|---|
| Baseline duration and path correct | A→X→I→R = 17 days, with Y float 2 and Z float 1 |
| Cost per day correct | X 45,000, Y 60,000, Z 40,000 |
| Non-critical compression is ruled out | Task 1 explains why Y and Z alone change nothing |
| Recalculation after each compression | The forward pass is redone, not assumed |
| New critical path identified | After one day of X, X and Z are both critical |
| Marginal cost pattern explained | The second day costs more than the first, with the reason |
| Fast-track risk is costed | 40% × one day of integration testing, expressed in money |
| Recommendation states a refusal | At least one option is explicitly ruled out with a reason |
Reflection¶
- The second day cost more than the first. Where would you expect the third day to sit, and what does that imply about compressing a schedule aggressively?
- Fast-tracking is cheaper than crashing here. What makes it nonetheless risky in a payment path specifically?
- Borrowing a specialist pushes another programme's delivery. Who should own that decision, and why is it not yours alone?
- If the board insists on the two days with no budget, what is the one thing you would protect, and how would you make that protection visible?
Check your numbers
- Baseline: A 0–3; X 3–11; Y 3–9; Z 3–10; I 11–15; R 15–17. Duration 17 working days.
- Critical path: A → X → I → R. Float: X 0, I 0, R 0, A 0; Y 2 days, Z 1 day.
- Cost per day: X 90,000 ÷ 2 = 45,000; Y 120,000 ÷ 2 = 60,000; Z 80,000 ÷ 2 = 40,000.
- First day: crash X by one day (45,000). New duration 16. Now X (7 days) and Z (7 days) are both critical — the path has split.
- Second day: must compress X again (45,000) and Z by one day (40,000) = 85,000, because X and Z are now parallel critical chains. New duration 15.
- Total to save two days: 130,000, with the marginal cost rising from 45,000 to 85,000 per day.
Full working is in the Advanced labs answer key.
Extension challenge¶
Build a cost-versus-duration curve for this project: plot the cheapest total compression cost for each achievable duration from 17 days down to the shortest achievable duration, and state the point at which further compression becomes impossible and why it cannot be bought. Then answer: if the board offered you a budget of exactly 100,000 for compression, what would you buy, and what would you tell them about the two days they asked for?