Project Management, CPM and PERT, and Engineering Ethics — ESE

Weightage: "Basics of project management" and "ethics and values in the engineering profession" are two items of the Paper I syllabus. Project management gives numerical questions that are quick when the network method is clear, and ethics gives short judgement questions where the best option is usually the safest, most honest one.

1. What a project is

A project is a temporary effort with a defined start and end, a unique output, and constraints of time, cost and quality. Its life cycle runs through initiation, planning, execution, monitoring and closure.

The work is broken into a work breakdown structure (WBS), a tree of deliverables and tasks. Each task gets a duration, resources and a predecessor, and these dependencies become the network diagram.

2. Network diagrams: activity on arrow and node

In the activity-on-arrow form, arrows are activities and circles are events. In the activity-on-node form, boxes are activities and arrows show dependence. Both give the same answers.

Two conventions: a dummy activity has zero duration and exists only to show a dependency, and every network has exactly one start and one end.

3. The forward and backward pass

For each activity define:

• ES earliest start, EF earliest finish $=ES+D$.
• LF latest finish, LS latest start $=LF-D$.

The forward pass takes each ES as the maximum EF of its predecessors. The backward pass takes each LF as the minimum LS of its successors.

Total float $=LS-ES=LF-EF$. It is the delay an activity can suffer without delaying the project. Free float is the delay that does not delay the next activity.

The critical path is the longest path through the network. Its activities have zero total float, and its length is the shortest possible project duration.

Worked example. A project has activities A (3 days), B (4 days, after A), C (2 days, after A) and D (5 days, after B and C).

• Path A-B-D: $3+4+5=12$ days.
• Path A-C-D: $3+2+5=10$ days.

The critical path is A-B-D, the project takes 12 days, and C has a total float of 2 days.

4. PERT: when durations are uncertain

PERT uses three estimates per activity: optimistic $a$, most likely $m$ and pessimistic $b$. It assumes a beta distribution, so:

$t_e=\frac{a+4m+b}{6},{\sigma }^2={\left(\frac{b-a}{6}\right)}^2$

The mean project duration is the sum of $t_e$ along the critical path, and the project variance is the sum of the critical-path variances. The chance of finishing by a target uses the normal distribution with $Z=(T-T_e)/\sigma$.

Worked example. An activity has $a=2$, $m=5$, $b=8$. Then $t_e=(2+20+8)/6=5$ and $\sigma =(8-2)/6=1$.

CPM versus PERT. CPM uses one deterministic time per activity and links time to cost, so it suits repetitive work such as construction. PERT uses three times, so it suits research and new work with uncertain durations.

5. Crashing and cost

Shortening a project by adding resources is crashing. Each activity has a normal time and cost and a crash time and cost, and the cost slope is:

$\text{cost slope}=\frac{\text{crash cost}-\text{normal cost}}{\text{normal time}-\text{crash time}}$

To crash the project, shorten only critical activities, and pick the one with the lowest cost slope first. As you crash, a second path can become critical, so recheck after every step. The least-cost duration balances rising direct cost against falling indirect cost (overheads).

6. Bar charts and earned value

A Gantt chart is a bar chart against time. It is simple and good for presenting a plan, but it does not show dependencies clearly.

Earned value management compares plan with progress using three numbers: planned value PV, earned value EV and actual cost AC.

Worked example. If PV = 100, EV = 80 and AC = 100, then SPI = 0.8 (behind schedule) and CPI = 0.8 (over budget).

7. Risk and resource management

Risk management means identifying risks, assessing probability and impact, planning a response (avoid, reduce, transfer or accept), and monitoring. Resource levelling smooths the demand on labour or machines by using float, without extending the project.

8. Engineering ethics

Ethics asks what an engineer owes to the public, the employer, the client and the profession. The recurring principles are:

• Public safety comes first. When an employer's wish conflicts with public safety, safety takes priority.
• Honesty and integrity in data, reports and claims; no falsifying results.
• Competence: undertake only work you are qualified to do.
• Confidentiality, subject to the public-safety limit.
• Avoiding conflict of interest, and disclosing it where it exists.
• Rejecting bribery and corruption.

Whistle-blowing is reporting a serious wrong inside an organisation to someone who can stop it. The usual guidance is to report internally first, document the facts, and go outside only if the danger is serious and internal routes fail.

Professional bodies such as the Institution of Engineers (India) and the Council of Architecture publish codes of conduct. Case studies such as the Bhopal gas disaster and the Challenger shuttle accident are standard examples of safety warnings ignored under schedule or cost pressure.

9. How to answer an ethics question

Look for the option that protects safety, tells the truth and follows the proper channel. Avoid extremes: neither silent compliance nor an immediate leak to the press is usually best. The preferred answer is normally to raise the concern formally, record it and escalate if it is not addressed.

Common traps

• Calling the shortest path critical. The critical path is the longest.
• Crashing a non-critical activity. It saves no project time.
• Using the PERT variance formula on the wrong path. Sum only critical-path activities.
• Mixing SPI and CPI. Schedule uses PV, cost uses AC.
• Treating confidentiality as absolute. Public safety overrides it.

Memory aids

• "a plus 4m plus b over 6": PERT mean.
• "Longest path is critical": zero float.
• "EV over PV for schedule, EV over AC for cost".

Summary

A project network turns tasks and dependencies into a critical path of zero float, found by a forward and backward pass. PERT adds three-time estimates for uncertain work, and crashing trades cost against time on critical activities.

Earned value measures progress with SPI and CPI. Ethics questions are answered by putting safety and honesty first and escalating through the proper channel.

Exam protocol

• Draw the network before any arithmetic.
• List all paths and sum their durations.
• Compute float only for non-critical activities.
• On ethics items, pick safety, truth, then proper channel.