Worst-Case Variance Bounded Sampling

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In Simple Words

Think of testing four different types of tires on race cars over a season. If one tire performs poorly early on, you want to stop putting it on drivers' cars to avoid accidents; however, if you stop using it completely, you will not gather enough data to mathematically prove its performance. Setting a strict safety floor guarantees that every tire gets tested on a minimum percentage of cars so statistical proofs remain valid.

Research question

Adaptive multi-armed bandit algorithms dynamically reduce assignment to underperforming treatment arms, which risks severe loss of statistical power and invalidates ex-ante frequentist standard error guarantees.

Participants

Parameterized for N = 4,000 subjects across 16 demographic strata in Jordan.

Study Design

Mathematical derivation establishing an upper bound lambda on estimator variance (lambda = 0.00125) to derive the algorithm tempering parameter gamma.

Results

Setting lambda = 0.00125 guarantees a worst-case standard error of 0.05 for treatment contrasts and a statistical power >= 0.80 for detecting effect sizes of 0.124 across N = 4,000 participants, enforcing a minimum assignment probability floor of 0.05 per treatment arm.

Takeaway

Select the upper variance parameter lambda based on required statistical power and sample size N to establish the minimum treatment assignment share gamma/k.

Source and citation

From the source

"Our experiment has the objective of maximizing participant outcomes... subject to the constraint of allowing for sufficiently precise inference on the effect of different treatments... We require frequentist guarantees on the precision of estimates."

Original source reference

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The original reference is reproduced as recorded. Full publication details have not been independently verified.

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