# What is the Sigma in standard deviation?

## What is the Sigma in standard deviation?

The unit of measurement usually given when talking about statistical significance is the **standard deviation**, expressed with the lowercase Greek letter **sigma** (σ). The term refers to the amount of variability in a given set of data: whether the data points are all clustered together, or very spread out.

## What does ∑ mean in statistics?

σ “sigma” = standard deviation of a population. Defined here in Chapter 3. ... **∑** “sigma” = summation. (This **is** upper-case sigma. Lower-case sigma, σ, **means** standard deviation of a population; see the table near the start of this page.)

## How do you find standard deviation in Six Sigma?

**The steps to calculating the standard deviation are:**

**Calculate**the mean of the data set (x-bar or 1. ...- Subtract the mean from each value in the data set2.
- Square the differences found in step 23.
- Add up the squared differences found in step 34.

## What is the relationship between standard deviation and mean?

The **standard deviation** (**SD**) measures the amount of variability, or dispersion, from the individual data values to the **mean**, while the **standard** error of the **mean** (SEM) measures how far the sample **mean** (average) of the data is likely to be from the true population **mean**. The SEM is always smaller than the **SD**.

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