estimation

# Estimation

## When to Use This Skill

Use this skill when:

- **Estimation tasks** - Working on estimation techniques including analogous, parametric, three-point, and expert judgment methods. provides effort, cost, duration, and complexity estimates for projects, features, and tasks
- **Planning or design** - Need guidance on Estimation approaches
- **Best practices** - Want to follow established patterns and standards

## Overview

Systematically estimate effort, cost, duration, and complexity using proven estimation techniques. Supports analogous, parametric, three-point (PERT), and expert judgment methods for projects, features, and tasks.

## What is Estimation?

**Estimation** is the process of forecasting the resources, time, and cost required to complete work. Good estimation balances:

- **Accuracy**: How close to actual results
- **Precision**: Consistency of estimates
- **Speed**: Time to produce estimates
- **Communication**: Shared understanding of uncertainty

### Estimation vs Commitment

| Concept | Definition | Use |
|---------|------------|-----|
| **Estimate** | Best guess given current knowledge | Planning, forecasting |
| **Commitment** | Promise to deliver by date/cost | Contracts, deadlines |
| **Target** | Desired outcome to aim for | Goals, objectives |

**Key principle:** Estimates are ranges with uncertainty, not single-point guarantees.

## Estimation Techniques

### Analogous Estimation (Top-Down)

Estimate based on similar past work:

| Step | Action |
|------|--------|
| 1 | Identify similar completed project/feature |
| 2 | Retrieve actual effort/cost/duration |
| 3 | Adjust for differences (complexity, team, technology) |
| 4 | Apply adjustment factor |

**Formula:**

```text
New Estimate = Historical Actual × Adjustment Factor

Example:
Similar project took 200 hours
New project is ~20% more complex
Estimate = 200 × 1.20 = 240 hours
```

**When to Use:** Early phases, limited detail, experienced teams with historical data

**Accu