“…If c 1,1 = c 2,1 = 0 (so that bothσ 2 1 andσ 2 2 are first-order unbiased for σ 2 ), then knowledge of the relative magnitudes of c 1,2 and c 2,2 would be helpful in determining which estimator has lower (second-order) bias. On the other hand, if c 1,1 = 0 but c 2,1 = 0 (so that onlyσ 2 1 is first-order unbiased), then it may still be the case that the constant c 1,2 is so prohibitively large thatσ 2 1 performs poorly in comparison withσ 2 2 for small batch sizes. In this case, it would be useful to determine which sample sizes guarantee Bias[σ 2 1 ] < Bias[σ 2 2 ].…”