For a dataset of nnn numbers, let S1=∑xiS_1 = \sum x_iS1=∑xi and S2=∑xi2S_2 = \sum x_i^2S2=∑xi2. What is the variance σ2\sigma^2σ2?
S2n−(S1n)2\frac{S_2}{n} - (\frac{S_1}{n})^2nS2−(nS1)2
S2n+(S1n)2\frac{S_2}{n} + (\frac{S_1}{n})^2nS2+(nS1)2
S1n−(S2n)2\frac{S_1}{n} - (\frac{S_2}{n})^2nS1−(nS2)2
S2−S1n\frac{S_2 - S_1}{n}nS2−S1