# Python statistics.variance() Method

Python statistics.variance() method is “used to calculate the variance of a sample dataset.” A variance measures the spread of a dataset and is calculated as the average of the squared differences between each data point and the mean of the dataset.

## Syntax

``statistics.variance(data, xbar=None)``

If the data has fewer than two values, StatisticsError raises.

## Parameters

1. data: This parameter is required when data is an array of valid Python numbers, including Decimal and Fraction values.
2. xbar: Where xbar is the mean of data, this parameter is optional. The mean is automatically calculated if this parameter is not given(none).

## Example 1: How to Use statistics.variance() Method

``````import statistics

dataset = [21, 19, 11, 21, 19, 46, 29]
output = statistics.variance(dataset)

print(output)``````

Output

``124.23809523809524``

## Example 2

Calculate the mean first and pass it to the variance() method as an argument.

``````import statistics

dataset = [21, 19, 11, 21, 19, 46, 29]
meanValue = statistics.mean(dataset)
output = statistics.variance(dataset, meanValue)

print(output)``````

Output

``124.23809523809524 ``

## Example 3: Use of xbar parameter in statistics.variance() method

``````import statistics

# creating a sample list
sample = (1.1, 1.2, 1.9, 2.1, 1.8, 2.2)

# calculating the mean of sample set
mean = statistics.mean(sample)

# calculating the variance of sample set
print("Variance of Sample set is % s"
% (statistics.variance(sample, xbar=mean)))

``````

Output

``Variance of Sample set is 0.2136666666666667``

## Example 4: statistics.StatisticsError: variance requires at least two data points

``````import statistics

# creating a sample list
sample = []

print(statistics.variance(sample))``````

Output

``statistics.StatisticsError: variance requires at least two data points``

That’s it.