Figure 2.

Scatter plots comparing the variance estimators. The upper-left plot shows the strong agreement between σ²($\widehat{\Delta }$_triplet) and our approximation σ²($\widehat{\Delta }$_pairwise). From the upper-right and the lower-left plots, it can be seen that both have similar correlation with ${\sigma }_{bootstrap}^2$($\widehat{\Delta }$_pairwise). Finally, the lower-right plot confirms that variance estimation under the assumption of independence can yield a large overestimation of the correct variance.