Confidence sequences for sampling without replacement
This work addresses uncertainty estimation for sequential sampling without replacement, which is incremental but provides practical improvements for statistical inference tasks.
The paper tackles the problem of quantifying uncertainty when sampling sequentially without replacement from a finite population, presenting a suite of tools for designing confidence sequences that improve on previous bounds and explicitly quantify the benefit of this sampling method.
Many practical tasks involve sampling sequentially without replacement (WoR) from a finite population of size $N$, in an attempt to estimate some parameter $θ^\star$. Accurately quantifying uncertainty throughout this process is a nontrivial task, but is necessary because it often determines when we stop collecting samples and confidently report a result. We present a suite of tools for designing confidence sequences (CS) for $θ^\star$. A CS is a sequence of confidence sets $(C_n)_{n=1}^N$, that shrink in size, and all contain $θ^\star$ simultaneously with high probability. We present a generic approach to constructing a frequentist CS using Bayesian tools, based on the fact that the ratio of a prior to the posterior at the ground truth is a martingale. We then present Hoeffding- and empirical-Bernstein-type time-uniform CSs and fixed-time confidence intervals for sampling WoR, which improve on previous bounds in the literature and explicitly quantify the benefit of WoR sampling.