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

Datetime:2016-08-23 01:04:46         Topic: Python          Share        Original >>

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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