Types of Estimation Technique

1. PERT (Program Evaluation and Review Technique)

• Focus: Project scheduling and time estimation, considering uncertainty.
• Method: Uses three estimates for each activity:
  • Optimistic (O): Best-case scenario.
  • Most Likely (M): Most probable duration.
  • Pessimistic (P): Worst-case scenario.
• Calculation:
  • Expected Time (TE) = (O + 4M + P) / 6 (weighted average)
  • Standard Deviation (SD) = (P - O) / 6 (measure of variability)
• Use: Helps determine the overall project duration and identify critical path activities.
• Software: PERT charts can be created with project management software like Microsoft Project, Primavera P6, and others.

2. WBS Method (Work Breakdown Structure)

• Focus: Breaking down a project into smaller, manageable components.
• Method:
  • Decompose the project into hierarchical levels of tasks and subtasks.
  • Estimate the effort (time, cost, resources) for each low-level task.
  • Aggregate the estimates up the hierarchy to get the total project estimate.
• Use: Provides a clear structure for estimation and helps ensure that all work is accounted for.
• Relationship to other methods: WBS can be used in conjunction with other estimation techniques like 3-point estimation or use-case points.

3. Use-Case Point Method

• Focus: Estimating software development effort based on the number and complexity of use cases.
• Method:
  • Identify and define use cases (how users interact with the system).
  • Classify use cases as simple, average, or complex.
  • Assign weights to each type of use case.
  • Calculate the unadjusted use-case points (UUCP).
  • Consider technical and environmental factors to adjust the UUCP and get the final use-case points.
  • Use historical data or industry benchmarks to convert use-case points into effort (e.g., person-hours).
• Use: Suitable for object-oriented software development projects.

4. 3-Point Estimation

• Focus: Improving estimation accuracy by considering a range of possible outcomes.
• Method: Similar to PERT, it uses three estimates:
  • Optimistic (O): Best-case scenario.
  • Most Likely (M): Most probable duration.
  • Pessimistic (P): Worst-case scenario.
• Calculation:
  • Triangular Distribution: TE = (O + M + P) / 3 (simple average)
  • Beta Distribution (PERT): TE = (O + 4M + P) / 6 (weighted average)
• Use: Can be applied to various types of projects and activities.

5. Wideband Delphi Technique

• Focus: Reaching a consensus among a group of experts on an estimate.
• Method:
  • A coordinator presents a problem or task to a group of experts.
  • Experts independently provide their estimates and justifications.
  • The coordinator summarizes the estimates and provides feedback to the experts.
  • Experts revise their estimates based on the feedback.
  • The process is repeated in multiple rounds until a consensus is reached or a satisfactory level of agreement is achieved.
• Use: Useful when there is high uncertainty or when expert judgment is needed.

Choosing the right estimation technique

The choice of estimation technique depends on factors such as:

• Project phase: Early phases may require less precise estimates than later phases.
• Project type: Different types of projects may be better suited to different techniques.
• Available data: Some techniques require historical data or expert judgment.
• Level of accuracy required: More complex techniques may provide more accurate estimates but require more effort.

It’s often beneficial to use a combination of techniques to get a more comprehensive and reliable estimate.