The variance of a set of value x1, x2, .... xn is given by which of the following formulae?
1
\(\rm \frac{\sum x^2}{n} - \rm \left(\frac{\sum x}{n}\right)^2\,\)
2
\(\rm \frac{\sum x^2}{n} - \rm \frac{\sum x}{n}\)
3
\(\rm \left(\frac{\sum x}{n}\right)^2 - \rm \frac{\sum x^2}{n}\)
4
\(\rm \left(\frac{\sum x}{n}\right)^2\)