99Ways

Conversion rate optimization, experimentation & analytics

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Diagram showing a true value metric passing through a calibration layer to an operational primary metric.
20 min

A/B Testing Metrics: Choose the Primary Metric Closest to Profit

The best A/B testing metric is usually the measurable outcome closest to incremental contribution per eligible visitor, user, or account. This guide separates true decision metrics, operational primaries, leading indicators, guardrails, and diagnostics—then maps ecommerce, subscription, pricing, lead-generation, marketplace, and cost-changing experiments to the metrics that should actually determine the winner.

Experimentation trust-chain diagram showing eligibility, a 50/50 hash split, control and zero-variant paths, identity persistence, exposure, outcome measurement, and a Zero Experiment calibration target
26 min

Experimentation System Audit: Can You Trust Your A/B Test Results?

An A/B result is only as trustworthy as the system that produced it. This audit framework examines eligibility, assignment, bucketing, identity persistence, exposure, sample-ratio mismatch, metric definitions, conversion windows, and statistical analysis. It also introduces the Zero Experiment: a production A/A calibration test designed to reveal whether the system creates lift where no treatment exists.