How to Calculate Standard Deviation & Variance in Python

🧠 Don’t miss out! Get FREE access to my Skool community — packed with resources, tools, and support to help you with Data, Machine Learning, and AI Automations! 📈 https://www.skool.com/data-and-ai-automations-4579 Need to measure how spread out your data is? In this tutorial, you'll learn how to calculate standard deviation and variance in Python using multiple methods—perfect for beginners in data science, statistics, or anyone analyzing numerical datasets. Code: https://ryanandmattdatascience.com/python-variance-and-standard-deviation/ 🚀 Hire me for Data Work: https://ryanandmattdatascience.com/data-freelancing/ 👨‍💻 Mentorships: https://ryanandmattdatascience.com/mentorship/ 📧 Email: [email protected] 🌐 Website & Blog: https://ryanandmattdatascience.com/ 🖥️ Discord: https://discord.com/invite/F7dxbvHUhg 📚 *Practice SQL & Python Interview Questions: https://stratascratch.com/?via=ryan 📖 *SQL and Python Courses: https://datacamp.pxf.io/XYD7Qg 🍿 WATCH NEXT Statistics for Data Science Playlist: https://www.youtube.com/playlist?list=PLcQVY5V2UY4LF-eHg0tfTpWHhgpX9XF4S Python Z-Score: https://youtu.be/QjG1ljFNF9U Python Cumulative Distribution Function: https://youtu.be/Oon9R40_Y20 Python Geometric Mean: https://youtu.be/zwF0-BjkExE In this video, I walk you through how to calculate variance and standard deviation for both population and sample data in Python. We start by covering the theory behind these statistical measures, including the key differences between population calculations (using n) and sample calculations (using n-1). I demonstrate manual calculations step-by-step so you understand exactly what's happening under the hood. After working through the math manually, I show you how to dramatically simplify these calculations using Python. We explore three different approaches: first doing it manually with basic Python code, then using NumPy's built-in functions (np.var and np.std), and finally leveraging the statistics library. Each method has its advantages, and I explain when you might want to use each one. The video includes real code examples that you can follow along with, starting from creating your dataset all the way through calculating both variance and standard deviation for population and sample data. By the end, you'll understand not just how to calculate these statistics in Python, but also when to use population versus sample formulas and which Python library is best for your specific use case. **Keywords:** variance python, standard deviation python, population variance, sample variance, numpy statistics, python statistics tutorial, variance calculation python, data analysis python TIMESTAMPS 00:00 Introduction & Overview 00:31 Population vs Sample Definition 01:42 Understanding Variance Calculation 03:02 Variance Calculation Example 04:32 Standard Deviation Explained 05:24 Setting Up Python Code 06:27 Example 1: Manual Population Variance 08:15 Manual Population Standard Deviation 09:00 Example 2: Manual Sample Variance 11:05 Using NumPy for Population Calculations 12:40 Example 4: NumPy Sample Calculations 15:09 Example 5: Statistics Library 16:40 Recap and Summary OTHER SOCIALS: Ryan’s LinkedIn: https://www.linkedin.com/in/ryan-p-nolan/ Matt’s LinkedIn: https://www.linkedin.com/in/matt-payne-ceo/ Twitter/X: https://x.com/RyanMattDS Who is Ryan Ryan is a Data Scientist at a fintech company, where he focuses on fraud prevention in underwriting and risk. Before that, he worked as a Data Analyst at a tax software company. He holds a degree in Electrical Engineering from UCF. Who is Matt Matt is the founder of Width.ai, an AI and Machine Learning agency. Before starting his own company, he was a Machine Learning Engineer at Capital One. *This is an affiliate program. We receive a small portion of the final sale at no extra cost to you.