Sample variance is a statistic, which measures the dispersion in a Sample.
Sample variance is used as an estimator of the population variance.
Sample variance s2 is given by the formula
s2 = i(1 to n)∑(xi-x̄)2/n-1
The reason the denominator has n-1 instead of n is because usage of n
in the denominator underestimates the population variance. Using n-1 makes the Sample Variance an unbiased estimator of the Population Variance.
The variance() function takes a sequence or an iterator as the parameter containing the sample data and returns the sample variance.
Python raises a StatisticsError if the data passed inside the variance() is empty
Python Example Program to find sample variance:
# import the statistics module
sampleData = [55,56,54,53,52,67,56,62,59]
sampleVariance = statistics.variance(sampleData)
print("Sample variance of the distribution is %.2f"%(sampleVariance))
Example Python program output that finds the sample variance:
Sample variance of the distribution is 23.11