Module ab_test 

A/B testing (Practical Statistics ch 3) — compare two variants’ conversion rates with a two-proportion z-test and a confidence interval on the lift. The honest output is “B beat A by 2.1pp [0.4pp, 3.8pp], p = 0.01” — effect size with uncertainty, not a bare “B wins”. Reuses the Normal CDF/quantile.

Structs

AbResult

Result of comparing two conversion rates.

Functions

ab_test

Two-proportion z-test. conv_* are conversions (successes), n_* the totals. alpha sets the CI/p-value (two-sided). None on invalid counts.