ISYS90050 · It Project and Change Management
Cost Estimation & Budgeting
Week 6 covers budgets and the cost taxonomy — tangible/intangible, direct/indirect and sunk costs — the defect-cost escalation curve, and the three estimation techniques: analogous (top-down), activity-based (bottom-up) and parametric. The examinable calculation is costing a task with overhead and personal-time loading, plus reconciling top-down and bottom-up estimates by iterative negotiation. Cost types and the loaded-cost calculation appear in short-answer and scenario items.
What this chapter covers
- 01Budget = a plan for allocating resources and a control baseline; project cost management = estimating, budgeting, controlling
- 02Cost types: tangible vs intangible, direct vs indirect, sunk cost (ignore in future decisions), overhead
- 03Defect-cost escalation across the SDLC (requirements 1x rising to post-release ~30x)
- 04Estimate accuracy bands: ROM (-50/+100%), budgetary (-10/+25%), definitive (-5/+10%)
- 05Analogous / top-down: expert judgment from a similar past project; quick, less accurate
- 06Activity-based / bottom-up: estimate each WBS activity and sum; accurate but time-intensive
- 07Parametric: a statistical rate (e.g. $ per line of code) times a parameter
- 08Costing a task: duration x rate x (1 + overhead%) x (1 + personal-time%); iterative budgeting by negotiation (R vs r)
Fully-loaded cost of a task with overhead and personal time
- +1Base cost with overhead = hours x rate x (1 + overhead). = 40 x 25 x 1.60. First 40 x 25 = $1,000; then x 1.60 = $1,600.
- +1Apply the personal-time allowance to the loaded base: fully-loaded = base x (1 + personal-time) = 1,600 x 1.10 = $1,760.
- +1Interpret. The raw effort ($1,000) understates the true cost by 76% once overhead and personal time are counted; budgeting on the raw rate alone would leave the task under-funded. The personal-time factor exists because an 8-hour day is not 8 productive hours.
Key terms
- Sunk cost
- Money already spent that cannot be recovered. It should not influence future invest-or-continue decisions — do not keep funding a failing project just because much has already been spent.
- Direct vs indirect cost
- Direct costs are tied to producing the project's products (salaries, project-specific hardware); indirect costs are incurred in doing the work but not tied to it (rent, electricity). Overhead spreads indirect costs across all work.
- Analogous (top-down) estimation
- An estimate based on expert judgment and the actual cost of a similar past project. Quick and inexpensive but less accurate; broken down top-to-bottom.
- Activity-based (bottom-up) estimation
- Estimating each work activity following the WBS and summing to a project total. More accurate when the team is experienced, but time-intensive and expensive to compile.
- Parametric estimation
- A statistical estimate using a rate per unit of a parameter (e.g. cost per line of code, adjusted for language and complexity) multiplied by the expected quantity.
- Iterative budgeting by negotiation
- Reconciling a PM's top-down requirement R with a team member's bottom-up estimate r (typically R << r): the PM is educated upward, the member relinquishes some padding, and both look for a more efficient method to close the gap.
Cost Estimation & Budgeting FAQ
Why load a task cost with overhead and personal time?
Because the raw hours x rate figure understates what the task really costs. Overhead spreads indirect costs (rent, power, shared services) across the work, and the personal-time allowance recognises that an 8-hour day is not 8 productive hours (breaks, admin). Loading both gives a realistic cost = duration x rate x (1 + overhead) x (1 + personal-time).
Should a sunk cost affect whether we continue a project?
No. A sunk cost is money already spent and unrecoverable, so it should be ignored in any forward-looking decision. Continuing a failing project merely because a lot has already been invested is the sunk-cost fallacy; base the decision on future costs and benefits.
When would I use top-down versus bottom-up estimation?
Use analogous (top-down) early, when detail is thin and you can lean on a similar past project — it is quick but less accurate. Use activity-based (bottom-up) once the WBS is detailed and the team is experienced — it is more accurate but time-consuming. In practice the two are reconciled through iterative budgeting by negotiation.
Can AI help me with cost estimation in ISYS90050?
Yes, as a study aid. Sia can drill loaded-cost calculations, quiz you on the cost taxonomy and estimate-accuracy bands, and rehearse the top-down/bottom-up reconciliation. Use it to learn the method; it does not do your graded assessment, and University of Melbourne academic-integrity rules apply — confirm details on Canvas.
Exam move
Make the loaded-cost calculation reflexive — hours x rate, then x (1 + overhead), then x (1 + personal-time) — and be able to show both the loaded base and the final figure. Memorise the cost taxonomy (tangible/intangible, direct/indirect, sunk, overhead) and the three estimation techniques with one advantage and one drawback each, since these are staple short-answer items. Keep the estimate-accuracy bands and the defect-cost escalation shape ready as supporting facts, and be able to explain iterative budgeting by negotiation. For the closed-book exam, rehearse the arithmetic without a calculator crutch and convert percentages to multipliers cleanly.
Working through Cost Estimation & Budgeting in ISYS90050? Sia is AskSia’s AI IT Project Management tutor — ask any ISYS90050 Cost Estimation & Budgeting question and get a clear, step-by-step explanation grounded in how ISYS90050 is taught and assessed. Read this chapter free, then take your hardest questions to Sia.
