Conversion Rate Uplift#
The increase in conversion rate attributable to a treatment versus control.
Important
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What it is#
Conversion-rate uplift measures the improvement (or decline) in conversion rate of a treatment (variant) relative to a control (baseline) — the headline success metric of an A/B test. It answers: by how much did the new variant move conversions versus the baseline?
Absolute vs relative#
With \(CR_A\) the control rate and \(CR_B\) the treatment rate, there are two distinct quantities:
Examples#
Positive — control 5%, treatment 6%: absolute uplift +1 point, relative uplift \((6-5)/5 = +20\%\).
Negative — control 10%, treatment 9.5%: absolute uplift −0.5 point, relative uplift \((9.5-10)/10 = -5\%\).
Why both matter#
The two can tell very different stories: a 1-point absolute uplift sounds tiny, but on a 2% baseline it is a 50% relative improvement. Quoting only one can mislead — report both.
How it drives A/B decisions#
Uplift is the primary metric, and the minimum detectable uplift / effect (MDE) — the smallest effect you want to catch given sample size, \(\alpha\) and power — sets how big the experiment must be. The decision rule: a significant positive uplift → ship; not significant → inconclusive; significant negative → stop or rethink. Whether the uplift is real or just noise is settled by a two-proportion z-test (frequentist) or the posterior probability of uplift (Bayesian).
Theme: A/B Testing & Experimentation · All terminology
Hint
Mind map — connected ideas
Posterior probability of uplift · A/B Testing · Conversion Rate (CR) · True Conversion Rate · Incremental Conversions · Traditional A/B Test (Fixed-Horizon A/B Test)
Hint
More in A/B Testing & Experimentation
A/B Testing · A/B/n Test · Bayesian Sequential Testing · Bayesian Stopping Rules · Fixed-Horizon Testing · Group Sequential Testing · Multivariate Test (MVT) · Online Experimentation Platforms · Optimizely · Risk of Peeking · Sequential Testing (also called sequential analysis) · Stopping Rules · Traditional A/B Test (Fixed-Horizon A/B Test) · Treatment Effect
See also
Source article Adapted (context, re-expressed) in our own words from: Conversion Rate Uplift (insightful-data-lab.com).