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

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

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
```

Python