Standard Deviation Calculator

Mean, variance and standard deviation of a data set.

Overview

Calculates population and sample standard deviation, variance, mean, and sum of squares across numerical datasets to quantify statistical dispersion.

Formula & Calculation Method

Sample SD (s) = sqrt([Sum(x_i - Mean)^2] / (n - 1)) | Population SD (sigma) = sqrt([Sum(x_i - Mean)^2] / N)

Uses Bessel's correction (n - 1) for sample data to provide an unbiased estimator of population variance.

Worked Example: Sample of 5 Data Points (10, 12, 14, 15, 19)

Inputs: Data Values: 10, 12, 14, 15, 19 (Sample n = 5)

  • Calculate sample mean: (10 + 12 + 14 + 15 + 19) / 5 = 70 / 5 = 14.0
  • Squared deviations: (10-14)²=16, (12-14)²=4, (14-14)²=0, (15-14)²=1, (19-14)²=25
  • Sum of squared deviations = 16 + 4 + 0 + 1 + 25 = 46.0
  • Sample variance = 46.0 / (5 - 1) = 46.0 / 4 = 11.5
  • Sample standard deviation = sqrt(11.5) = 3.391

Summary: Mean = 14.0 | Sample SD = 3.39 | Population SD = 3.03 | Variance = 11.5

Common Use Cases

  • Financial Volatility: Measure investment risk and stock price volatility (beta/Sharpe ratio).
  • Quality Control Manufacturing: Ensure industrial component dimensions remain tightly grouped around target tolerances.
  • Scientific Research: Quantify measurement uncertainty and experimental variance in laboratory studies.

Frequently Asked Questions

What is Bessel's correction in standard deviation?

Dividing by n - 1 instead of n for sample data, which corrects for the mathematical bias of underestimating population variance.

What does a high standard deviation mean?

A high standard deviation indicates that data points are widely dispersed and spread out across a broad range of values.

How does variance differ from standard deviation?

Variance is the average of squared deviations; standard deviation is the square root of variance, restoring the original unit of measurement.

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