A/B Test Statistical Significance Calculator

About

A/B Test Statistical Significance Calculator
                                                                                                                
  Find out if your A/B test results are real — or just luck. Enter your control and variant data and get instant
   p-values, confidence intervals, and relative uplift. No signup, no data collection, no network requests.
  Everything runs locally in your browser.

  What it does

  This extension gives you a lightweight A/B test calculator that lives in your browser toolbar. Click the icon
  from any tab to:

  - Enter visitor and conversion counts for your control and variant groups
  - Choose your confidence level (90%, 95%, or 99%)
  - Get a clear verdict: statistically significant or not
  - See the p-value, relative uplift, control rate, and variant rate at a glance
  - View the confidence interval for the true difference in conversion rates

  Results appear instantly. No page loads, no waiting, no context switching.

  Why install it

  If you run A/B tests — on landing pages, ad creatives, email subject lines, checkout flows, or anything else —
   you need to check statistical significance before making decisions. Most people either skip this step or have
   to dig through bookmarks to find a calculator.

  This extension puts the calculator one click away, on every tab. You can check results during a meeting, while
   reviewing analytics, or while writing a test report — without leaving the page you're on.

  Who it's for

  - Growth marketers and CRO specialists running split tests
  - Performance marketers evaluating ad creative tests
  - Product managers reviewing experiment results
  - Data analysts who want a quick sanity check
  - Anyone who runs A/B tests and wants to make decisions based on evidence, not guesswork

  How it works

  The calculator uses a two-proportion z-test — the standard frequentist method for comparing two conversion
  rates. It calculates:

  - p-value: The probability your result happened by chance, assuming no real difference between control and
  variant. A p-value below your threshold (e.g., 0.05 for 95% confidence) means the result is statistically
  significant.
  - Relative uplift: The percentage difference between variant and control conversion rates.
  - Confidence interval: The range within which the true difference in conversion rates likely falls.

  It also warns you when your sample size is too small (fewer than 30 conversions per group), so you know when
  results may be unreliable.

  Privacy

  This extension collects no data. It makes no network requests. All calculations happen locally in your
  browser. There are no analytics, no tracking, and no third-party scripts.

  Built by Jarrah Agency

  Jarrah is a performance marketing agency that builds paid media and CRO programs on rigorous testing
  methodology. This calculator is the same one available on our website at jarrah.agency — packaged as an
  extension for quick access.