# Bayesian A/B Test Calculator

Analyze your A/B test results with Bayesian statistics. Get probability to win, expected lift, risk analysis, and clear recommendations - no signup required.

## Frequently Asked Questions

### Why Bayesian instead of frequentist statistics?

Bayesian analysis gives you direct probability statements like "There's a 95% chance variation beats control." It also allows for continuous monitoring without inflating false positive rates, and naturally incorporates prior knowledge when available.

### What does "expected loss" mean?

Expected loss quantifies the potential cost of making the wrong decision. If the expected loss of implementing the variation is 0.05%, it means on average you'd lose 0.05 percentage points of conversion rate if the variation is actually worse. This helps you make risk-aware decisions.

### What is Sample Ratio Mismatch (SRM)?

SRM occurs when the actual traffic split differs significantly from the expected split (e.g., 50/50). This can indicate bugs in your experiment setup, bot traffic, or data collection issues. The calculator checks for SRM automatically and warns you if detected.

### How much data do I need?

There's no fixed minimum, but Bayesian analysis becomes more reliable with more data. As a rule of thumb, aim for at least 100 conversions per variant for meaningful results. The calculator will suggest continuing testing if there isn't enough data to make a confident decision.

### Is my data stored anywhere?

No. All calculations happen entirely in your browser. Your data never leaves your device and is not stored or transmitted anywhere.

[Open calculator](https://www.pagent.ai/tools/ab-test-calculator)