Module 2: Approaches to Software Estimation

Duration: 115 minutes (10:35am - 12:30pm)

This module explores various approaches to software estimation, focusing on analogy-based estimation, software size estimation techniques, and selecting appropriate methods for different project types.

Table of contents
  1. Learning Objectives
  2. Quick Exercise 2.1: Function Point Analysis (30 minutes)
    1. Background
    2. Task 1: Count Function Points (20 minutes)
      1. External Inputs (EI) - Users entering data
      2. External Outputs (EO) - Reports and displays
      3. External Inquiries (EQ) - Search functions
      4. Internal Files (ILF) - Data stored by system
      5. External Files (EIF) - Data from other systems
    3. Task 2: Convert to Effort Estimate (10 minutes)
  3. Advanced Exercise 2.2: Analogical Estimation (35 minutes)
    1. Background
    2. Task 1: Similarity Analysis (15 minutes)
    3. Task 2: Calculate Analogical Estimates (20 minutes)
      1. Method 1: Most Similar Project
      2. Method 2: Weighted Average (Top 3)
  4. Module 2 Summary
    1. Key Takeaways
    2. Quick Reference
    3. Next Steps

Learning Objectives

By the end of this module, you will be able to:

  • Select appropriate estimation approaches based on project characteristics
  • Apply analogy-based estimation using historical project data
  • Calculate software size using Lines of Code (LOC), Use Case Points, and Function Points
  • Understand when to use gross vs. detailed estimation approaches
  • Combine multiple estimation techniques for improved accuracy

Quick Exercise 2.1: Function Point Analysis (30 minutes)

Background

You’re estimating a Document Management System for a law firm.

System Requirements:

  • Document upload and storage
  • Document search and retrieval
  • User access control and permissions
  • Document versioning and history
  • Basic reporting (usage statistics)
  • Integration with email system

Task 1: Count Function Points (20 minutes)

Identify and classify the main functions:

External Inputs (EI) - Users entering data

Function Complexity Weight Count Total FP
Document Upload Average 4 1 4
User Registration Simple 3 1 3
Permission Settings Complex 6 1 6
EI Subtotal       13

External Outputs (EO) - Reports and displays

Function Complexity Weight Count Total FP
Usage Reports Average 5 1  
Document List Simple 4 1  
EO Subtotal       ___

External Inquiries (EQ) - Search functions

Function Complexity Weight Count Total FP
Document Search Average 4 1  
User Lookup Simple 3 1  
EQ Subtotal       ___

Internal Files (ILF) - Data stored by system

Function Complexity Weight Count Total FP
Document Repository Complex 15 1  
User Profiles Simple 7 1  
ILF Subtotal       ___

External Files (EIF) - Data from other systems

Function Complexity Weight Count Total FP
Email System Simple 5 1  
EIF Subtotal       ___

Total Unadjusted Function Points: _____ FP

Task 2: Convert to Effort Estimate (10 minutes)

Using productivity rate of 12 FP per person-month for web applications:

Estimated Effort: ___ FP ÷ 12 FP/PM = ___ person-months

With 25% contingency: ___ PM × 1.25 = ___ person-months

Advanced Exercise 2.2: Analogical Estimation (35 minutes)

For participants who complete the quick exercise early

Background

Use historical project data to estimate a Mobile Banking App.

Historical Projects:

Project Type Size (KLOC) Team Duration Effort (PM)
Web Banking Financial 45 6 10 months 48
Mobile Shopping E-commerce 35 5 8 months 32
Insurance Portal Financial 52 7 12 months 65
Mobile Wallet FinTech 28 4 6 months 20

New Project: Mobile Banking App

  • Estimated size: 40 KLOC
  • Team: 5 developers
  • Technology: React Native, Node.js
  • Complexity: High (security, compliance)

Task 1: Similarity Analysis (15 minutes)

Rate similarity to new project (1-10 scale):

Historical Project Technology Match Size Match Complexity Match Team Match Overall Similarity
Web Banking 7 (same domain) 9 (45 vs 40) 9 (high security) 8 (6 vs 5)  
Mobile Shopping 8 (mobile) 8 (35 vs 40) 6 (lower complexity) 10 (5 vs 5)  
Insurance Portal 6 (financial) 7 (52 vs 40) 8 (compliance) 7 (7 vs 5)  
Mobile Wallet 9 (FinTech mobile) 6 (28 vs 40) 9 (security) 9 (4 vs 5)  

Task 2: Calculate Analogical Estimates (20 minutes)

Method 1: Most Similar Project

Selected: ______

Direct scaling: ___ PM × (40 KLOC / ___ KLOC) = _____ PM

Method 2: Weighted Average (Top 3)

Project Weight Historical PM Size Ratio Adjusted PM
1st: _____ ___/10 _____ 40/_____ _____
2nd: _____ ___/10 _____ 40/_____ _____
3rd: _____ ___/10 _____ 40/_____ _____

Weighted Average: _____ PM

Final Estimate Range: ___ to ___ person-months

Module 2 Summary

Key Takeaways

  1. Function Points: Size-independent measurement based on user functionality
  2. Analogical Estimation: Most reliable when you have similar, recent projects
  3. Multiple Methods: Cross-check estimates using different approaches
  4. Similarity Matters: Technology, domain, and team experience affect accuracy

Quick Reference

Function Point Weights:

  • External Inputs: Simple=3, Average=4, Complex=6
  • External Outputs: Simple=4, Average=5, Complex=7
  • External Inquiries: Simple=3, Average=4, Complex=6
  • Internal Files: Simple=7, Average=10, Complex=15
  • External Files: Simple=5, Average=7, Complex=10

Analogical Estimation:

  • ✅ Use projects within last 2-3 years
  • ✅ Consider technology similarity
  • ✅ Adjust for team experience differences
  • ✅ Account for complexity variations

Next Steps

Continue to Module 3: Development Effort and Cost Estimation to learn about COCOMO and cost calculations.