Explain the reasons for incorporating dummy activities in a network diagram. In what way do these differ from the normal activities?
Explain the basic logic of arrow networks.
How does the PERT technique help a business manager in decision-making?
The Correct Answer and Explanation is:
Reasons for Incorporating Dummy Activities in a Network Diagram
Dummy activities are used in Arrow Diagramming Method (ADM) or Activity-on-Arrow (AOA) network diagrams. They serve the following purposes:
- Maintain Logical Relationships: Dummy activities ensure the correct representation of precedence relationships between activities, especially when two activities share the same start and end events but are dependent on different predecessors.
- Avoid Ambiguity: Without dummy activities, it might appear that unrelated tasks are dependent on each other, leading to inaccurate scheduling and planning.
- Clarify Dependencies: They clarify which activity must be completed before another begins, even if it doesn’t require time or resources.
- Preserve Uniqueness: In AOA networks, each activity must have a unique representation; dummy activities help distinguish different relationships using zero duration arrows.
Difference from Normal Activities:
- Duration: Dummy activities have zero duration, while normal activities consume time and resources.
- Representation: Dummies are shown as dashed arrows, while normal activities use solid arrows.
- Purpose: Dummy activities serve only to maintain logic; normal activities represent actual tasks or work.
Basic Logic of Arrow Networks
In Arrow Networks (AOA):
- Arrows represent activities (tasks or jobs to be performed).
- Nodes (circles) represent events (starting or ending points of activities).
- Each activity is defined by its starting and ending event numbers.
- The network flows left to right, showing the sequence of work.
- The main goal is to identify the critical path, which determines the shortest time in which the project can be completed.
PERT Technique and Managerial Decision-Making
Program Evaluation and Review Technique (PERT) helps managers plan and control complex projects by analyzing tasks, durations, and dependencies.
How PERT Helps in Decision-Making:
- Time Estimates: PERT uses three estimates—optimistic (O), most likely (M), and pessimistic (P)—to compute an expected time (TE) using: TE=O+4M+P6TE = \frac{O + 4M + P}{6} This gives a more realistic timeline under uncertainty.
- Identifying Critical Path: Helps identify which sequence of tasks (critical path) directly impacts project completion. Managers can prioritize resources accordingly.
- Risk Management: By quantifying uncertainty, PERT helps in anticipating delays, adjusting plans, and minimizing risks.
- Better Resource Allocation: PERT allows forecasting resource needs and optimizing their use to avoid bottlenecks.
- Improved Communication: A visual timeline aids in coordination among teams and stakeholders.
In summary, PERT enables managers to plan efficiently, foresee potential issues, make informed scheduling decisions, and improve project success rates.
