How to Calculate Standard Deviation Easily

Standard deviation is an important statistical concept that measures the amount of variation or dispersion of a set of data values from its mean value. It is commonly used in business, science, and engineering to evaluate data and make informed decisions. In this article, we will explain how to calculate standard deviation in simple terms, step by step.

What is Standard Deviation?

Standard deviation is a measure of how spread out a set of numbers is around the mean. It tells us how much the data deviates from the average value, and how much the individual data points differ from each other. In other words, it indicates the degree of variability or dispersion of the data set. The standard deviation is typically denoted by the symbol σ (sigma) for a population and s for a sample.

Standard Deviation FormulaSource:

How to Calculate Standard Deviation Step by Step

To calculate standard deviation, you need to follow these steps:

  1. First, find the mean or average value of the data set by adding up all the values and dividing by the total number of values.
  2. Mean FormulaSource:

  3. Next, subtract the mean from each data point to get the deviations from the mean.
  4. Then, square each deviation to eliminate negative values and make them all positive.
  5. Square FormulaSource:

  6. Sum up all the squared deviations.
  7. Sum FormulaSource:

  8. Divide the sum of squared deviations by the total number of values minus one (n-1) to get the variance.
  9. Variance FormulaSource:

  10. Finally, take the square root of the variance to get the standard deviation.
  11. Standard Deviation FormulaSource:

Example Calculation of Standard Deviation

Let us take the following data set:

6, 7, 8, 9, 10

First, we find the mean value:

Mean = (6 + 7 + 8 + 9 + 10) / 5 = 8

Next, we calculate the deviations from the mean:

Deviations = (6 – 8), (7 – 8), (8 – 8), (9 – 8), (10 – 8) = -2, -1, 0, 1, 2

Then, we square each deviation to get:

Squared deviations = 4, 1, 0, 1, 4

Sum of squared deviations = 10

Variance = 10 / (5-1) = 2.5

Standard deviation = √2.5 = 1.5811 (approx.)

Types of Standard Deviation

There are two types of standard deviation:

  • Population standard deviation (σ) – used when the data set represents the entire population.
  • Sample standard deviation (s) – used when the data set is a representative sample of the population.

Why is Standard Deviation Important?

Standard deviation is important because it helps us to:

  • Understand the spread and variability of data.
  • Assess the reliability and accuracy of data.
  • Compare different sets of data.
  • Determine the confidence interval and margin of error.
  • Identify outliers or anomalies in the data set.


In conclusion, standard deviation is a useful statistical measure that provides valuable insights into the variability and spread of data. By following the steps outlined in this article, you can easily calculate standard deviation and use it to make informed decisions and draw meaningful conclusions from your data.

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