Excel : Understanding standard deviation and choosing the right function (P, S, Standard)

In Excel, the use of standard deviation can quickly give rise to doubt, as several functions coexist. Knowing when to use ECARTYPE.P or ECARTYPE.S is essential for reliable analyses.

Remember that standard deviation is an indicator that measures the dispersion of data in relation to the mean. Let’s take a simple example: if you’re tracking your company’s monthly sales, standard deviation lets you know how much those sales fluctuate from month to month.

In practice :

ECARTYPE.P applies when the entire population is available.
ECARTYPE.S (formerly ECARTYPE.STANDARD) is used when working with a sample.

Understanding standard deviation

Definition

The standard deviation (σ) measures the average deviation of the values in a data set from the mean (μ). It is calculated by taking the square root of the variance. The higher the standard deviation, the more dispersed the data.

Calculation formula

Calculate the mean.
Subtract this mean from each value and square it.
Average these squares.
Extract the square root of the result.

This indicator is fundamental to descriptive statistics and data analysis, as it reveals the variability of observations.

Why is the standard deviation important?

It enables us to compare several distributions and identify whether the data are homogeneous or dispersed.
In finance, it is used to measure the volatility of returns.
In marketing, it is used to analyze the consistency of survey responses.
It is also used to calculate confidence intervals and test hypotheses.

To expand your data analysis skills, see also:

The different standard deviation functions in Excel

ECARTYPE.P

Used to calculate the standard deviation of an entire population.

ECARTYPE.S

Corresponds to the standard deviation of a sample. It replaces the former ECARTYPE.STANDARD.

ECARTYPE.PEARSON

A rarer function that also accepts text and logical values as arguments.

ECARTYPE.STANDARD

Former formula, now replaced by ECARTYPE.S. Still used in some teaching environments.

Standard deviation formulas: sample vs. population

For a sample

Formula :

In Excel → use =ECARTYPE.S(range).

For a population

Formula:

In Excel → use =ECARTYPE.P(range).

How to use standard deviation in Excel

Simple entry in a cell

For example:

Application to a range of data

Example: =ecartype.s(b

Analysis of real data

In finance :

This is used to measure the stability or volatility of monthly sales.

Use cases for standard deviation

Finance: analyze market volatility and portfolio stability.
Marketing: evaluate variations in customer responses and refine segmentation.
Science and industry: control variability in production processes.

Advanced questions on standard deviation

Comparing several samples: useful for determining which group is the most homogeneous.
Statistical tests: such as Levene’s test to compare variances.
Interpretation: a low standard deviation indicates little dispersion, a high standard deviation indicates great variability.
Visualizations: histograms and boxplots help interpret results.

Excel versions and compatibility

Excel 2013, 2016, 2019

2013: introduction of Power View and chart recommendations.
2016: real-time co-editing and integration with OneDrive.
2019: cartographic charts, 3D formulas and enriched analyses.

Excel on the Mac vs. Excel for the Web

Mac: similar to the Windows version, with SEARCHX and pivot tables.
Web: practical for online collaboration, but limited advanced features.

Conclusion

Standard deviation is an essential statistical tool for understanding data dispersion.

Remember:

ECARTYPE.P → whole population.
ECARTYPE.S → sample.

Properly used, it allows you to analyze variability, compare distributions and make data-driven decisions.