The Three Questions | A/B Testing for Product Managers

A/B Testing for Product Managers

The Four Deaths

What a Test Can and Cannot Tell You

Why "Let's Just Test It" Is Often Wrong

The Shape of a Good Test

What This Course Covers

The Three Questions

When to Just Ship It

Test, or Go and Talk to Someone?

Exercise 1: Triage Your Test Ideas

Why "We Think This Will Improve Conversion" Isn't One

The Four-Part Hypothesis

Saying in Advance What Would Make You Wrong

One Change or Several?

Exercise 2: Write a Real Hypothesis

The Four Numbers

The Calculation, Worked Through

Why Most Tests Are Too Small

The Weekly Cycle Rule

Exercise 4: Do the Arithmetic Before You Build

Before You Turn It On

What to Check on Day Two

The Six Things That Invalidate a Running Test

Exercise 5: Set Up Properly

What "Significant" Actually Means

Effect Size and the Range

The Flat Result

When the Result Contradicts What You Believed

Exercise 6: Read a Result Properly

Winning Isn't the Same as Worth Shipping

Exercise 7: Decide and Record

Slicing Until Something Wins

Novelty and Primacy

Contamination, Mismatch and Survivorship

Exercise 8: Audit Your Own Results

Five Situations Where Testing Won't Help

What to Do With Too Little Traffic

Knowing When to Stop

Exercise 9: Diagnose Your Testing Programme

Final Project: Design, Run and Report One Real Test

Before You Build: Deciding Whether to Test

Before You Build: Writing and Stress-Testing a Hypothesis

Before You Build: Choosing Your Metrics

Before You Build: Sample Size and Duration

Running It: Pre-Launch Review

Reading It: Reading a Result Honestly

Reading It: Auditing for the Six Lies

Afterwards: The Test Readout

Checking Yourself: Is Testing Right for Your Situation?

Glossary: Words Explained

Lesson 1

The Three Questions

Ask these in order. Most ideas fail at one of them, and failing one is a complete answer, you don't need to consider the others.

THE THREE QUESTIONS

What will I do if it wins?

If the answer is "ship it," good, continue.

If the answer is "ship it anyway, regardless," stop.

You don't need a test to do what you were going to do.

What will I do if it loses?

If the answer is "not ship it," good, continue.

If the answer is "ship it anyway," stop. Same reason.

Can I detect the effect I'm hoping for?

Work out the sample size (Chapter 4) before building.

If it needs 14 weeks and you have 3, stop.

A test that can't detect your expected effect will return "flat" whether or not the change worked.

Question 3 Is the One Teams Skip

Sample size gets calculated after the test is built, or after it's been running for two weeks and looks flat. By then you've spent the money. Doing the arithmetic first, it takes ten minutes, is the single highest-return habit in this whole course, because it's the one that prevents wasted build time rather than just wasted analysis.