A/B/n Test#
An experiment comparing more than two variants simultaneously.
Important
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What it is#
An A/B/n test generalises the two-arm A/B test to several variants at once — A vs B vs C vs … n — of a page, app or feature, splitting traffic across all of them to find which scores best on a chosen metric (conversion, click-through, engagement).
How it works#
Pick a control (A, the current design), build variants B, C, D…; randomly split users across them; track the metric; and use a statistical test (two-proportion z-test, chi-square or a Bayesian model) to pick the winner. Testing button text — “Buy Now” vs “Shop Now” vs “Get Yours Today” vs “Order Now” — sends each of four equal groups one variant and compares conversions.
Why and when#
It tests many ideas in one experiment rather than a sequence of A/B tests, which is faster when you have several candidate designs and enough traffic for a winner-takes-all verdict.
The costs#
Two prices. Traffic: a 50/50 split becomes 33/33/33 and beyond, so each arm gets less data and significance takes longer. And the multiple-comparisons problem: every extra variant is another chance for a false positive, so the family-wise error rate climbs unless corrected. It also reveals less about element interactions than a multivariate test.
Example#
Optimising newsletter sign-ups across four calls to action at 25% traffic each, after two weeks A converts 5%, B 6%, C 7.5% and D 5.2%. C is the significant winner and ships.
Theme: A/B Testing & Experimentation · All terminology
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Mind map — connected ideas
A/B Testing · Multivariate Test (MVT) · Traditional A/B Test (Fixed-Horizon A/B Test) · Bandit Algorithms · Two-Proportion Z-Test · Type I Error
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More in A/B Testing & Experimentation
A/B Testing · Bayesian Sequential Testing · Bayesian Stopping Rules · Conversion Rate Uplift · 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: A/B/n Test (insightful-data-lab.com).