# How to calculate the standard deviation from the mean

**Introduction**

Standard deviation is a widely used statistical measure that helps in understanding the spread of data points around the mean value. It indicates how much the individual values in a data set deviate from their mean. In this article, we will discuss how to calculate the standard deviation from the mean.

**Steps to Calculate Standard Deviation from the Mean**

**1. Start by collecting your data:** The first step is to gather all the available data points of interest. For instance, if you are working with a dataset of test scores, collect all the individual scores.

**2. Calculate the mean (average):** The mean is calculated by adding up all the values in your dataset and dividing by the total number of items. Using test scores as an example:

**Mean = (Sum of all test scores) / (Total number of students)**

**3. Subtract the mean from each value and square the result:** Now, for each value in your dataset, subtract its corresponding mean value and square it. The squared result implies that we disregard any negative differences; it also gives more weight to larger deviations.

**Squared deviation = (Data point – Mean)^2**

**4. Calculate the average squared difference:** Add up all squared deviations obtained in step 3 and divide by the total number of values in your dataset. This calculation gives us variance.

**Variance = (Sum of squared deviations) / (Total number of values)**

**5. Find the square root of variance:** Lastly, take the square root of variance to obtain standard deviation.

**Standard Deviation = √(Variance)**

**6. Interpret your results:** Analyze what you have just computed, considering how spread out your data points are from their mean value.

**Example Calculation:**

Imagine a set of five test scores – {45, 66, 57, 49, 67}. To calculate standard deviation:

**1. Find Mean:**

**Mean =** (45 + 66 + 57 + 49 + 67) / 5 = 56.8

**2. Subtract mean from each value and square the result:**

**(45 – 56.8)^2 =** 139.24

**(66 – 56.8)^2 =** 85.64

**(57 – 56.8)^2 =** 0.04

**(49 – 56.8)^2 =** 60.84

**(67 – 56.8)^2 =** 104.04

**3. Calculate average squared difference (variance):**

**Variance =** (139.24 + 85.64 + 0.04 + 60.84 +104.04) / 5 = 77.96

**4. Find square root of variance:**

**Standard Deviation =** √(77.96) ≈ 8.83

So, the standard deviation for our dataset is approximately 8.83.

**Conclusion**

Calculating the standard deviation plays a crucial role in statistical analysis by providing insights into the dispersion of data around its mean value while accounting for outliers’ potential effect on the data set interpretation.

Once you understand these concepts, you can quickly determine the data’s reliability and variability to make informed decisions in various fields such as finance, science, and engineering.