Analogous Estimation

Overview

Analogous estimation (also called top-down estimation) uses data from similar past projects to estimate the duration, effort, and resources needed for a new project.

How It Works

Process

1. Identify similar completed projects
2. Review actual time and resources used
3. Adjust for differences (size, complexity, team)
4. Apply adjusted estimates to new project
5. Document assumptions and basis

Requirements

• Historical project data
• Similar project characteristics
• Documented past performance
• Understanding of differences

When to Use

Ideal Scenarios

• Early project phases (limited detail)
• Similar projects to past work
• Quick estimates needed
• High-level planning
• Budget ballpark figures

Less Suitable

• Novel projects (no analogues)
• Highly detailed estimates needed
• Significant differences from past work
• Final budget approval

Advantages

• Fast: Quick to generate estimates
• Low cost: Minimal effort required
• Experience-based: Leverages real data
• Useful early: Works with limited information
• Organizational learning: Builds knowledge base

Disadvantages

• Accuracy varies: Depends on similarity
• Requires history: Needs past project data
• Subjective: Judgment in selecting analogues
• May miss details: Top-down approach
• Bias risk: Pattern matching errors

Best Practices

1. Select True Analogues

• Similar scope and complexity
• Same or similar technology
• Comparable team size and skills
• Similar constraints
• Recent enough to be relevant

2. Adjust for Differences

• Team experience level
• Technology changes
• Scope variations
• Resource availability
• External factors

3. Use Multiple References

• Don't rely on single project
• Average across several analogues
• Weight by similarity
• Consider range of outcomes

4. Document Assumptions

• Which projects used as basis
• What adjustments made
• Why those adjustments
• Confidence level
• Known risks

Integration with Time Tracking

Build Historical Database

• Track all project time
• Categorize by type and characteristics
• Document complexity factors
• Record actual vs. estimated
• Note lessons learned

Improve Estimates Over Time

• Compare analogous estimates to actuals
• Identify systematic bias
• Refine adjustment factors
• Build estimation accuracy

Create Reference Library

• Standard project profiles
• Typical durations by project type
• Complexity multipliers
• Team productivity factors

Common Patterns

By Project Size

• Small: 1-3 months
• Medium: 3-6 months
• Large: 6-12 months
• Enterprise: 12+ months

Adjustment Factors

• Team experience: 0.7-1.3x
• Technology newness: 1.0-2.0x
• Complexity: 0.8-1.5x
• Stakeholders: 1.0-1.4x

Combining with Other Methods

• Analogous + Expert judgment: Validate estimates
• Analogous + Parametric: Use both top-down and model-based
• Analogous + Bottom-up: Reconcile differences
• Analogous + Three-point: Refine range

Example

Past Project: Website redesign, 3 developers, 4 months

New Project: Similar website redesign

• Same technology
• 2 developers (vs. 3)
• More features

Estimate: 4 months × (3/2 team ratio) × 1.2 (more features) = ~7 months