Collect the data values
Compute the mean: mean = (sum of all values) / n
Compute each deviation from the mean: deviation = value − mean
Square each deviation: squared deviation = (value − mean)²
Sum the squared deviations: sumsq = Σ (value − mean)²
If finding population variance: variance = sumsq / n
If finding sample variance: variance = sumsq / (n − 1)
(Optional) Standard deviation: sqrt(variance)