Find the mean of the data set
Subtract the mean from each data value
Square each difference
Add all the squared differences
Divide by the number of values for population variance
Divide by one less than the number of values for sample variance
Use the formula: population variance = Σ(x – μ)² / N
Use the formula: sample variance = Σ(x – xÌ„)² / (n – 1)