A/B Test Calculator: run a/b test calculations online. Formula, assumptions, and interpretation guide.
Conversion rate: p = conversions / visitors
Pooled proportion: p_pool = (conv_A + conv_B) / (visitors_A + visitors_B)
Z-statistic: z = (p_B − p_A) / √[p_pool × (1−p_pool) × (1/n_A + 1/n_B)]
Minimum detectable effect (MDE): MDE = z_α × √(2 × p × (1−p) / n) — the smallest uplift your test can reliably detect.