# Statistical Functions in Python | Set 2 ( Measure of Spread)

Statistical Functions in Python | Set 1(Averages and Measure of Central Location)

Measure of spread functions of statistics are discussed in this article.

**1. variance()** :- This function calculates the variance i.e **measure of deviation of data, more the value of variance, more the data values are spread**. Sample variance is computed in this function, assuming data is of a part of population. If passed argument is empty,** StatisticsError** is raised.

**2. pvariance()** :- This function computes the **variance of the entire population**. The data is interpreted as it is of the whole population. If passed argument is empty,** StatisticsError** is raised.

`# Python code to demonstrate the working of ` `# variance() and pvariance()` ` ` `# importing statistics to handle statistical operations` `import` `statistics` ` ` `# initializing list` `li ` `=` `[` `1.5` `, ` `2.5` `, ` `2.5` `, ` `3.5` `, ` `3.5` `, ` `3.5` `]` ` ` `# using variance to calculate variance of data` `print` `(` `"The variance of data is : "` `,end` `=` `"")` `print` `(statistics.variance(li))` ` ` `# using pvariance to calculate population variance of data` `print` `(` `"The population variance of data is : "` `,end` `=` `"")` `print` `(statistics.pvariance(li))` |

Output:

The variance of data is : 0.6666666666666667 The population variance of data is : 0.5555555555555556

**3. stdev()** :- This function returns the **standard deviation ( square root of sample variance )** of the data. If passed argument is empty,** StatisticsError** is raised.

**4. pstdev()** :- This function returns the population **standard deviation ( square root of population variance )** of the data. If passed argument is empty,** StatisticsError** is raised.

`# Python code to demonstrate the working of ` `# stdev() and pstdev()` ` ` `# importing statistics to handle statistical operations` `import` `statistics` ` ` `# initializing list` `li ` `=` `[` `1.5` `, ` `2.5` `, ` `2.5` `, ` `3.5` `, ` `3.5` `, ` `3.5` `]` ` ` `# using stdev to calculate standard deviation of data` `print` `(` `"The standard deviation of data is : "` `,end` `=` `"")` `print` `(statistics.stdev(li))` ` ` `# using pstdev to calculate population standard deviation of data` `print` `(` `"The population standard deviation of data is : "` `,end` `=` `"")` `print` `(statistics.pstdev(li))` |

Output:

The standard deviation of data is : 0.816496580927726 The population standard deviation of data is : 0.7453559924999299

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