Five methods of Estimating Activity Duration

📘 Five Methods of Estimating Activity Duration

Estimating activity duration is a key part of project planning. Different methods are used depending on data availability, project size, and uncertainty.

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🔹 1. Expert Judgment 👨‍💻

👉 Definition:

Estimation based on the experience and knowledge of experts.

🔑 Features:

• Quick and simple
• Relies on past experience
• Useful when data is limited

💡 Example:

A senior developer estimates that coding a login module will take 3 days.

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🔹 2. Analogous Estimation 📊

👉 Definition:

Uses data from similar past projects to estimate duration.

🔑 Features:

• Fast and cost-effective
• Less accurate than detailed methods

💡 Example:

Previous website project took 5 days for testing, so a similar estimate is used.

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🔹 3. Parametric Estimation 📐

👉 Definition:

Uses mathematical formulas and productivity rates to calculate duration.

🔑 Formula:

Duration = Work / Productivity Rate

💡 Example:

• Work = 200 lines of code
• Productivity = 50 lines/day 👉 Duration = 200 ÷ 50 = 4 days

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🔹 4. Three-Point Estimation (PERT) ⭐

👉 Definition:

Uses three different estimates to handle uncertainty.

• O (Optimistic) → Best case
• M (Most Likely) → Normal case
• P (Pessimistic) → Worst case

🔑 Formula:

TE = (O + 4M + P) / 6

💡 Example:

• O = 2, M = 5, P = 8 👉 TE = (2 + 4×5 + 8)/6 = 5 days

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🔹 5. Bottom-Up Estimation 🧩

👉 Definition:

Estimate each small task (work package) and then combine them.

🔑 Features:

• Highly accurate
• Time-consuming
• Used in detailed planning

💡 Example:

• UI Design = 2 days
• Coding = 5 days
• Testing = 3 days 👉 Total = 10 days

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🔹 6. Quick Comparison Table

Method	Accuracy	Speed	Best Use
Expert Judgment	Medium	Fast	When expert available
Analogous	Low–Medium	Very Fast	Early planning
Parametric	Medium–High	Medium	When data available
Three-Point (PERT)	High	Medium	Uncertain tasks
Bottom-Up	Very High	Slow	Detailed projects

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🔹 7. Important Exam Points

• PERT is most important (formula-based)
• Bottom-up = most accurate
• Analogous = quick but less precise
• Expert judgment = experience-based
• Parametric = formula-based

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🔹 8. Short Summary

• There are five main methods to estimate activity duration:

  1. Expert Judgment
  2. Analogous Estimation
  3. Parametric Estimation
  4. Three-Point (PERT)
  5. Bottom-Up Estimation

• Choice depends on project complexity and data availability

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🔹 9. Quick Exam Answer (2–3 lines)

The five methods of estimating activity duration are expert judgment, analogous estimation, parametric estimation, three-point (PERT), and bottom-up estimation. These methods vary in accuracy and are selected based on project needs and available data.

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🔹 10. Likely Exam Questions

1. List the five methods of estimating activity duration.
2. Explain expert judgment with example.
3. What is analogous estimation?
4. Describe parametric estimation with formula.
5. Explain PERT technique.
6. Which method is most accurate and why?