The statistical measure of standard deviation measures the degree of variance or dispersion in a set of data values. It provides valuable information about how spread out the data points are around the mean (average) of the data set. In other words, it helps us understand the degree of variability or deviation from the average.

The standard deviation can be used to compare datasets recorded at various scales because it is expressed in the same units as the original data. It enables you to determine the level of variability present in a dataset, verify the validity of statistical findings, spot outliers, and reach well-informed conclusions about the distribution of data.

In this article, we will discuss the concept of standard deviation, find steps of standard deviation and the importance of standard deviation also explain standard deviation with the help of detailed examples.

What isStandard Deviation?

The degree of variance or dispersion within a collection of data is measured statistically using the standard deviation. It gives a number that expresses how far apart the data points are from the dataset’s mean (average).

By computing the square root of the variance, one may mathematically determine the standard deviation. By averaging the squared deviations between each data point and the mean, the variance is calculated. The negative values are removed by squaring the differences, which treats the deviations as positive values.

Standard Deviation: Finding steps

To find the standard deviation, you can take assistance from a std calculator or follow the below steps for manual calculations.

  • Determine the mean of the data set by summing all the values and dividing by the total number of values.
  • To find every data points subtract the mean and square the result. This step is important because it ensures that the deviations from the mean are positive and prevents them from canceling each other out.
  • The average of the squared deviations acquired in step 2 should be calculated. The variance is a name for this number. 
  • To find the standard we take the square root of variance. This step is necessary to revert to the original units of the data.
  • The standard deviation makes it possible for you to comprehend how data points vary from the mean. A lower standard deviation shows that the data points are closer to the mean and more densely grouped, while a higher standard deviation indicates greater variability.
  • Standard deviation is widely used in various fields, including finance, economics, psychology, and natural sciences. It helps in assessing risk, determining the reliability of statistical results, comparing data sets, and making decisions based on the spread of data.
  • It is worth noting that standard deviation is influenced by outliers, extreme values that significantly differ from the rest of the data. Therefore, it is essential to consider the context and the presence of outliers when interpreting the standard deviation.

Importance of Standard Deviation

The importance of standard deviation lies in its ability to provide valuable insights into data variability and distribution. Here are several key reasons why standard deviation is important:

  • The measure of Variability: The spread or dispersion of data points around the mean is measured by the standard deviation. It gives us a sense of how widely apart individual data points are from the mean and serves as a gauge of dataset variability.
  • Assessing Data Quality: By calculating the standard deviation, we can evaluate the consistency and reliability of the data. A low standard deviation suggests more accurate and dependable observations since it shows how closely the data points are packed around the mean.
  • Risk Assessment: Standard deviation is widely used in risk analysis and finance. In investment and portfolio management, standard deviation helps assess the volatility or risk associated with an asset or a portfolio of investments. A higher standard deviation implies a greater potential for fluctuation in returns and higher risk.
  • Comparing Data Sets: Standard deviation enables the comparison of different datasets. By comparing the standard deviations of two or more sets of data, we can determine which dataset has greater variability or spread, allowing for meaningful comparisons and insights.
  • Normal Distribution Analysis: Standard deviation plays a crucial role in understanding the properties of the normal distribution. It helps determine the range of values within certain standard deviation intervals and is utilized in statistical inference and hypothesis testing.
  • Outlier Detection: Standard deviation can be used to identify outliers, which are data points that significantly deviate from the mean. Data points that fall outside a certain number of standard deviations from the mean are often considered outliers and may warrant further investigation.
  • Decision-Making and Prediction: Standard deviation provides a quantitative measure of uncertainty or variation. It assists in decision-making processes by considering the level of risk or uncertainty associated with different options. Additionally, the standard deviation is utilized in predictive models to assess the reliability and accuracy of predictions.

Example of Standard Deviation

We discuss here two types of examples one for population and the other for sample standard deviation.

Example 1:

Find the population standard deviation of 15, 25, 30, 35, 36, and 41.


Step 1: Evaluate the mean of the given data

Mean of population data = ∑x/n = [15 + 25 + 30 + 35 + 36 + 41]/6= 182/6 = 30.33

Step 2: Now find the typical distance of each data point & the mean and square of each deviation. 

Data values (xixi – µ (xi – µ)2
88 – 30.33 = -22.33(-22.33)2 = 498.62
2222 – 30.33 = –8.33(-8.33)2 = 69.38
2626 –30.33= -4.33 (4.33)2 = 18.75
2525 – 30.33 = -5.33(-5.33)2 = 28.41
3030 – 30.33 = 0.33(0.33)2 = 0.108
3333 – 30.33= 2.67(2.67)2 = 7.13

Step 3: Add the deviations to find the statistical sum of squares.

∑ (xi – µ)2 = 498.62+69.38+18.75+28.41+0.108+7.13

∑ (xi – µ)2 = 622.398

Step 4: Now divide the sum of squares by n.

∑ (xi – µ)2/n = 622.398/6

∑ (xi – µ)2/n = 103.733

Step 5: Take the square root.

√ [∑ (xi – µ)2/n] = √103.733

√ [∑ (xi – µ)2/n] = 10.18

Example 2:

Find the sample standard deviation of 15, 10, 5, 25, and 30.


Step 1: Evaluate the mean of the population.

Meanof sample data = ∑x/n= [15 + 10 + 5 + 25 + 30]/5
                                       = 85/5
                                       = 17

Step 2: Now find the typical distance of each data point & the mean and square of each deviation. 

Data values (xi)   xi – x̅  (xi – x̅)2
1212 – 17 = -5   (-5)2 = 25
1515 – 17 = -2  (-2)2 = 4
1818 – 17 = 1(1)2 = 1
2020 – 17 = 3 (3)2 = 9
2525 – 17 = 8  (8)2 = 64

Step 3: Add the deviations to find the statistical sum of squares.

∑ (xi – x̅)2 = 25 + 4 + 1 + 9 + 64

∑ (xi – x̅)2 = 103

Step 4: Divide the sum by n – 1.

∑ (xi – x̅)2 / n-1 = 103/5-1

∑ (xi – x̅)2 / n-1 = 103/4

∑ (xi – x̅)2 / n-1 = 25.75

Step 6: Take the square root.

√ [∑ (xi – x̅)2 /n-1] = √25.75

√ [∑ (xi – x̅)2 /n-1] = 5.0744


In this article, we delve into the concept of standard deviation, exploring its calculation steps and its significance. Through detailed examples, we further elucidate the concept. After thoroughly studying this article, readers will be equipped to confidently explain and defend the concept of standard deviation.

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