Click here to purchase the entire book in PDF format. Variance the variance of a population of N measurements is denoted $s^{2}$. This is the mean of the squares of the deviations of the measurements. $s^{2} = \frac{\Sigma (x_{i}-m)^{2}}{N}$ The variance of a sample of $n$ measurements is denoted $s^{2}$ This is the sum of the squared deviations of the measurements about the sample mean divided by $(n-1)$ CHECK THIS - SHOULDN'T IT BE n AND NOT n-1?