* 53 pages; supersedes the preprint arXiv:2004.08657; v2 corrects an
erroneous claim about SingleShuffle and newly adds Theorem 24 and Appendix F
for SingleShuffle Access Paper or Ask Questions
* We have discovered a mistake in the main result. The quantity on the
RHS of (3) is not equal to the variance of estimator (2) when the sampling
rule is designed adaptively as we do. There will be further cross-product
terms which are now dominant terms. Therefore, although our bound is correct
for (3), it no longer implies bound of the variance of (2) Access Paper or Ask Questions
