---
title: "What is Null Hypothesis?"
url: https://fibr.ai/glossary/null-hypothesis
description: "The null hypothesis assumes no significant difference between two versions in testing. It’s rejected only if data shows clear evidence of improvement."
last_updated: 2026-05-05T11:56:50.599561+00:00
---
The null hypothesis is an assumption in testing that there’s no significant difference or effect between two versions. It’s the default belief until data proves otherwise.

In A/B testing, the null hypothesis assumes both versions perform the same. If data shows a clear improvement in one version, the null hypothesis is rejected.

It’s a scientific way to avoid bias and ensure results are based on evidence, not assumptions.

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