<b>Average order value tests fail significance checks because the math is wrong, not the metric.</b>

<b>Average order value tests fail significance checks because the math is wrong, not the metric.</b>
AOV and revenue-per-session are ratio metrics — the denominator (sessions) is itself random. A naive t-test understates variance and hands you false wins.
— Use the delta method or bootstrap to get honest confidence intervals on ratios.
— Revenue is also heavy-tailed: one whale moves the mean, so winsorize or cap.
The lift looks real until you price in the whale.
Read the number, not the story. [delta method · winsorized 99th pct]