Guide · Program strategy · 1 min read

CRO hypothesis: How to write one that teaches you something

Write CRO hypotheses that link evidence, change, audience and expected effect, so every A/B test teaches you something. Includes a template and good and bad examples.

“Let’s test a red button” is an idea. A hypothesis explains why the change should matter, for whom, and how you’ll know. That difference decides whether a test teaches you anything.

The template

Because we observed [evidence from research or analytics], we believe [specific change] for [audience or segment] will [increase/decrease] [primary metric], because [the mechanism: what changes in the user’s mind or effort]. We’ll know by [primary metric, guardrails, MDE and decision rule].

Download or fill in the hypothesis template.

Good and bad examples

Weak: “Changing the CTA colour will increase conversions.” No evidence, no audience, no mechanism. If it loses, you’ve learned nothing.

Strong: “Because 31 of 120 exit-survey answers mention unexpected delivery costs, and recordings show shoppers pausing at the shipping line, we believe showing the delivery cost and date on the product page for all UK visitors will increase checkout completion, because removing a late surprise reduces perceived risk. We’ll know by checkout completion rate (MDE 8% relative), with average order value and returns as guardrails.”

(Numbers in this example are illustrative.)

Checklist

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A testable hypothesis…

Why the mechanism matters

If the test loses, the mechanism tells you what to doubt. Was the evidence wrong (people don’t actually care about delivery cost)? Or was the execution weak (they didn’t notice the new line)? Each answer points to a different next test.

From hypothesis to roadmap

In the WXM Architect phase, every hypothesis is scored with PXL and the highest-scoring ones go to Validate.

Frequently asked questions

What is a hypothesis in CRO?

A testable statement that links observed evidence to a specific change and a predicted effect on a chosen metric, with the reason you expect it to work.

Sources

  1. WXM: the Wave Experimentation Model. Wavesy. Accessed 4 November 2026.
  2. PXL: A Better Way to Prioritize Your A/B Tests. CXL. Accessed 4 November 2026.

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