FA-74559 / Experiment statistics / Member archive

Post-exposure metric window: All users share the earliest exposure as window start · case 04

Late-exposed users contribute almost nothing because their window closed before they arrived.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

events are [user, day, value]; exposures maps user -> first exposure day. A user's metric sums values of their events with exposure_day <= day < exposure_day + window_days. Every exposed user appears, even with no qualifying events; unexposed users are dropped. Return sorted [user, total].

Why this case matters

Counting pre-exposure activity dilutes effects; dropping silent users biases means upward.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
each user has their own window	`[["a", 1], ["b", 0]]`	`[["a", 1], ["b", 1]]`	Failed

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