FA-74544 / Experiment statistics / Member archive

Post-exposure metric window: Activity before exposure is counted · case 04

Treatment effects are diluted by behaviour that happened before users saw the change.

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
pre-exposure activity is excluded	`[["a", 7]]`	`[["a", 2]]`	Failed

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