# A/B Buddy — Sample Size & Power Calculator > Sample size and power calculator for designing statistically valid A/B experiments. (iPhone/iPad app by Evan Miller.) - Source: https://appshunter.io/ios/app/ab-buddy/id1446129030 (this page in markdown: same URL + `.md`) - Developer: [Evan Miller](https://appshunter.io/developer/329911740) - Category: Utilities, Reference - Price: Free with in-app purchases - Rating: 4.00/5 from 4 App Store ratings - Age rating: 4+ - Requires: iOS 13.0 · 2 MB - Languages: American English - Released: 2019-01-15 - Data updated: 2026-06-01 - Monetization: free with in-app purchases - User reviews in markdown: https://appshunter.io/ios/app/ab-buddy/id1446129030/reviews.md ## What is A/B Buddy? If you're planning to run an experiment – either on the web or in real-life – it's critical to collect the right amount data so that you know the experiment results are scientifically valid. A/B Buddy is a sample-size calculator that helps you design A/B experiments with a quick slide of a finger. It uses a power-analysis formula to tell you exactly how many subjects, or users, that you'll need in an experiment in order to detect a statistically significant difference between two groups. Because if you have too few users in the experiment, you'll never see any difference between "A" and "B"; if you have too many enrolled, the experiment will never end. A/B Buddy tells you exactly the right number. How does it work? Let's say your current conversion rate is 10%, and you want to see if a proposed change from the design team can boost that number up to 12% – that is, a 20% lift in the conversion rate. Simply pop open A/B Buddy, set the Baseline conversion rate to 10%, and the Minimum Detectable Effect to 20%, and your answer is waiting for you at the top of the screen. A/B Buddy includes a Share button, which links to a web page displaying your sample size calculation. Your numbers, however, remain 100% private – all the information is stored in the URL fragment, and is never transmitted to any servers. By default, A/B Buddy uses the most common statistical thresholds: 5% for the significance level (false-positive rate), and 80% for the power level (ability to detect the Minimum Detectable Effect). Power users can adjust these values after unlocking the Pro Features in-app purchase. But most users will find the defaults adequate for their needs. Questions? Suggestions? Ideas? Feedback is always welcome at emmiller@gmail.com ## Key features - Sample size calculation for A/B tests - Power analysis formula - Adjustable baseline conversion rate - Minimum Detectable Effect setting - Shareable calculation links - Privacy-focused data handling ## Pricing and in-app purchases Base price: Free. **One-time purchases** | Purchase | Price | Type | | --- | --- | --- | | Pro Features | $8.99 | one-time | ## Frequently asked questions about A/B Buddy ### What is A/B Buddy used for? A/B Buddy is a sample-size calculator designed to help you determine the exact number of participants needed for your A/B experiments. This ensures your results are scientifically valid and that you can detect statistically significant differences between groups. ### How does A/B Buddy calculate sample size? It uses a power-analysis formula. You input your current conversion rate and the desired minimum detectable effect (e.g., a 20% lift), and the app calculates the required number of subjects or users. ### Is my data private when using A/B Buddy? Yes, your data remains 100% private. The app stores all calculation information within the URL fragment, which is then shared. No data is transmitted to any servers. ### What are the default statistical thresholds in A/B Buddy? By default, A/B Buddy uses a 5% significance level (false-positive rate) and an 80% power level (ability to detect the minimum detectable effect). These are common thresholds for statistical analysis. ### Can I adjust the statistical thresholds in A/B Buddy? Yes, advanced users can adjust these values by unlocking the Pro Features through an in-app purchase. However, the default settings are adequate for most users' needs. ### Does A/B Buddy have ads? No, A/B Buddy does not contain advertisements. The app is free to use, with an optional in-app purchase for advanced features. ### What devices is A/B Buddy compatible with? A/B Buddy is compatible with iPhones, iPads, and iPods. It is designed for iOS devices. ### How often is A/B Buddy updated? The latest version, 1.1.0, was released on April 14, 2020. The app was initially released on January 15, 2019, suggesting periodic updates for improvements and bug fixes. ## Version history (last 3 releases) ### 1.1.0 — 2020-04-14 • Full support for Dark Mode • A/B Buddy now requires iOS 13 or later ### 1.0.1 — 2019-01-21 • NEW glossary of terms explaining what each number represents • NEW allow Minimum Detectable Effects of up to 100% (previous limit was 50%) • Fix a bug when copying the subject count ### 1.0 — 2018-12-12 No release notes. ## Apps similar to A/B Buddy | App | Rating | Price | Category | | --- | --- | --- | --- | | [OctoCheck](https://appshunter.io/ios/app/octocheck/id6471322030) | 5.0 (1) | Free | Utilities | | [Analytics Rating in App Store](https://appshunter.io/ios/app/analytics-rating-in-app-store/id6708226267) | 5.0 (2) | Free | Utilities | | [SnapDrafter](https://appshunter.io/ios/app/snapdrafter/id6746699358) | 5.0 (2) | Free | Utilities | | [Unee - Your first AI bestie](https://appshunter.io/ios/app/unee-your-first-ai-bestie/id6753331145) | 3.9 (11) | Free | Utilities | | [Clean Master - Del Photo&Video](https://appshunter.io/ios/app/clean-master-del-photo-and-video/id6472238249) | — | Free | Utilities | | [NewOaks](https://appshunter.io/ios/app/newoaks/id6476862904) | — | Free | Utilities | --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-01.*