project-estimation（项目估算）

Project Estimation

Table of Contents

• Overview
• When to Use
• Quick Start
• Reference Guides
• Best Practices

Overview

Accurate project estimation determines realistic timelines, budgets, and resource allocation. Effective estimation combines historical data, expert judgment, and structured techniques to minimize surprises.

When to Use

• Defining project scope and deliverables
• Creating project budgets and timelines
• Allocating team resources
• Managing stakeholder expectations
• Assessing project feasibility
• Planning for contingencies
• Updating estimates during project execution

Quick Start

Minimal working example:

# Three-point estimation technique for uncertainty

class ThreePointEstimation:
    @staticmethod
    def calculate_pert_estimate(optimistic, most_likely, pessimistic):
        """
        PERT formula: (O + 4M + P) / 6
        Weighted toward most likely estimate
        """
        pert = (optimistic + 4 * most_likely + pessimistic) / 6
        return round(pert, 2)

    @staticmethod
    def calculate_standard_deviation(optimistic, pessimistic):
        """Standard deviation for risk analysis"""
        sigma = (pessimistic - optimistic) / 6
        return round(sigma, 2)

    @staticmethod
    def calculate_confidence_interval(pert_estimate, std_dev, confidence=0.95):
        """
        Calculate confidence interval for estimate
        95% confidence ≈ ±2 sigma
        """
        z_score = 1.96 if confidence == 0.95 else 2.576
// ... (see reference guides for full implementation)

Reference Guides

Detailed implementations in the references/ directory:

Best Practices

✅ DO

• Use multiple estimation techniques and compare results
• Include contingency buffers (15-25% for new projects)
• Base estimates on historical data from similar projects
• Break down large efforts into smaller components
• Get input from team members doing the actual work
• Document assumptions and exclusions clearly
• Review and adjust estimates regularly
• Track actual vs. estimated metrics for improvement
• Include non-development tasks (planning, testing, deployment)
• Account for learning curve on unfamiliar technologies

❌ DON'T

• Estimate without clear scope definition
• Use unrealistic best-case scenarios
• Ignore historical project data
• Estimate under pressure to hit arbitrary targets
• Forget to include non-coding activities
• Use estimates as performance metrics for individuals
• Change estimates mid-project without clear reason
• Estimate without team input
• Ignore risks and contingencies
• Use one technique exclusively