Estimate sample size for a two-sided test of two conversion rates.
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When to use A/B Test Sample Planner
Plan a fixed-horizon experiment using a baseline conversion rate and minimum relative lift. The calculation uses a normal approximation with equal-sized variants.
How to use this tool
- Enter baseline rate and minimum detectable relative lift
- Choose confidence and power
- Enter daily eligible visitors to estimate duration
Before you use the result
This estimate assumes independent observations, equal allocation and a fixed end point. Low event rates, repeated peeking and multiple comparisons need a more careful statistical design.
Open the downloaded file or export before relying on it. Keep the original so you can compare quality, recover data or try different settings. Use only material you have permission to process.
Questions about A/B Test Sample Planner
Can I stop as soon as one variant looks ahead?
A fixed-horizon plan does not support repeated significance checks. Use a suitable sequential method if early stopping is part of the design.
Where are my files or inputs processed?
Files, pasted text and CSV inputs for this tool are processed in your browser. The tool does not upload them to WebInMarketing. Clear the page when finished on a shared device.
What are the input limits?
File tools accept up to 25 MB per file and 60 MB per batch, with at most 20 files. PDF rendering is limited to 40 pages and 20 megapixels per page. Image output is limited to 20 megapixels. CSV tools accept up to 10 MB and 20,000 rows. Large jobs may need a desktop browser.