Standard Deviation in Finance: Volatility Explained

Standard deviation measures how spread out investment returns are around their average, and this explainer shows how investors use it to interpret stock-return risk. You’ll learn the standard deviation formula, why deviations are squared, how variance fits into the calculation, and how to read one- and two-standard-deviation ranges. I walk through a five-year stock-return example with 15%, -5%, 25%, 5%, and 10% to calculate a 10% annual standard deviation step by step. The video also applies the concept to 50 years of S&P 500 returns and explains three important limitations: upside and downside count equally, results depend on historical data, and market tails can be fatter than a bell curve suggests. Whether you’re learning statistics or evaluating investment risk, this video gives you a practical framework for calculating and interpreting standard deviation.

Chapters
0:00 – What Is Standard Deviation?
0:26 – How Standard Deviation Measures Spread
0:49 – Calculate the Mean and Deviations
1:38 – Why We Square Deviations
2:03 – Variance, Square Root, and the Formula
2:43 – Reading Standard Deviation with a Bell Curve
3:15 – Standard Deviation in Real Market Data
3:57 – 3 Blind Spots of Standard Deviation

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*Disclosure: This is not financial advice and should not be taken as such. The information contained in this video is an opinion. Some of the information could be wrong. This channel is owned and operated by Portfolio Constructs LLC. Some of the links above are affiliate links, meaning, at no additional cost to you, I will earn a commission if you click through and make a purchase.