Won the Test, But	Consider	Decision
Effect is +0.3%	Maintenance cost, code complexity	Often not worth it
It doubles page weight	Effects on slower connections you didn't sample	Investigate before shipping
A guardrail moved badly	The primary win may be borrowed from elsewhere	Don't ship, understand it first
It only won for new users	Existing users may be harmed	Ship to new users only, if you can
It contradicts your product direction	Short-term metric vs longer-term position	Judgement call, make it explicitly
It's expensive to maintain	Ongoing cost against one-off gain	Cost it out properly

The Decision Is Yours, Not the Tool's

A green light in a testing tool is evidence, not a verdict. The most common failure in mature testing programmes is teams that ship everything that turns green, accumulating complexity for a series of tiny gains and never asking whether the product got better overall.

A/B Testing for Product Managers

Module 1Why Most A/B Tests Waste Three Weeks

Module 2Is This Even Worth Testing?

Module 3Writing a Hypothesis You Can Be Wrong About

Module 4Choosing the Metric

Module 5How Long It Needs to Run

Module 6Running It Without Ruining It

Module 7Reading the Result

Module 8Deciding and Shipping

Module 9The Six Ways Tests Lie

Module 10When A/B Testing Is the Wrong Tool

Module 11Final Project: Design, Run and Report One Real Test

Module 12Appendix: The Prompt Library

Module 13Glossary: Words Explained

Winning Isn't the Same as Worth Shipping