🤖 AI Summary
Directional replicability studies address whether at least $ r geq 2 $ out of $ n $ independent studies exhibit effects in the same direction, without prespecifying the direction a priori. Existing methods combine two-sided p-values by merging left- and right-tailed p-values and doubling the result to correct for double-testing, yet this approach is overly conservative.
Method: Under the assumptions that effect sizes are symmetrically distributed about zero and studies are independent, we prove that the factor-of-two correction is unnecessary while still strictly controlling the family-wise error rate (FWER). We propose a correction-free directional consistency testing framework grounded in one-sided p-value combination and directional inference theory.
Results: The proposed method substantially improves statistical power—particularly in multi-center validation, meta-analysis, and replicability assessment—offering a more sensitive and theoretically rigorous tool for evaluating directional replicability.
📝 Abstract
Directional replicability addresses the question of whether an effect studied across $n$ independent studies is present with the same direction in at least $r$ of them, for $r geq 2$. When the expected direction of the effect is not specified in advance, the state of the art recommends assessing replicability separately by combining one-sided $p$-values for both directions (left and right), and then doubling the smaller of the two resulting combined $p$-values to account for multiple testing. In this work, we show that this multiplicative correction is not always necessary, and give conditions under which it can be safely omitted.