**Calculating the standard deviation helps you explain your AVERAGE calculation**

**The AVERAGE**The average is a very common Statistical calculation. It's a statistical measure that represents the central tendency of a set of values

**The Standard Deviation**This calculation will highlight variations in the average

## Analysing this situation

Let's say you have a classroom with 10 students

- For the first exam, all the students had the same mark; 5
- For the second exam, the result is totally different
- 5 students have the mark 0
- 5 students have the mark 10

The average is the same for both exams (5), but of course, the analysis can't be the same. This is where **the standard deviation will help you to have a better analysis of your average results**.

## Calculation of the standard deviation

- Write the function =STDEV
- Select your range of cells

=STDEV(B2:B11) => 0

=STDEV(C2:C11) => 5.27

**What do these results mean?**

**0**means that all values in the series are equal to the average. There is no gap (or deviation) between the average and the values of the series.- On the other hand, for the second series,
**the result is very far from 0**and even exceeds the average value.

In other words, **the standard deviation represents the dispersion of the data around the **average. The more the result is close to 0, the more the data is centered on the average; 0 means no dispersion at all

## Several formulas in Excel, why?

As you have certainly noticed, there are several functions in Excel that calculate **the standard deviation.**

In Excel 2010, Microsoft engineers asked significant statisticians to improve the speed of the calculations and their accuracy for large numbers of data.

- The STDEV.P is based on the entire population (N). This function replaces the former STDEVP function.
- The STDEV.S is based on a sample (N-1). This function replaces the former STDEV function.

The difference between the 2 calculation modes concerns **the sample and, therefore, the divisor**. If you calculate the standard deviation with the entire population, the divisor will equal N (with N, the number of elements). When you calculate for a sample, the divisor is N-1.

## Tutorial video

## Related Articles

- Bollinger Bands with Excel
- TOP 10 Most Useful Statistical Functions for Data Analysis
- What is the Most Common Value in your Excel document.

Jin John

19/02/2021 @ 12:05

This is very knowledgeable information for students, I gave you a favor in the form of an online calculator.