## Introductory Statistics 9th Edition

s^2=$(∑m^2 f-( ((∑〖mf)〗^2 )/n))/(n-1)$ The formula above is the basic formula to calculate the population and sample variances for grouped data, and $s^2$ is the sample variance. Thus we can see that sample variance is the mean of the squared deviations of x values from the mean.