[1/5] A/B Testing Fundamentals: What Is A/B Testing?
Learn the one skill that separates junior from senior marketers
What Is A/B Testing?
⏱️ 2-min read
You want to move from “I think this will work” to “I know this works because I tested it.”
That shift separates marketers who guess from marketers who get promoted.
The Basic Idea
A/B testing compares two versions of something to see which performs better. Version A is your original. Version B is your new idea. You split your traffic between both versions and measure what happens.
Think of it like trying two different subject lines in an email campaign. Half your list gets subject line A. The other half gets subject line B. Whichever gets more opens wins.
The same logic applies to landing pages, ad copy, pricing pages, checkout flows, and basically anything your customers interact with.
Why This Matters for Your Career
Every senior marketing role expects you to run experiments. Job descriptions say things like “data driven decision making” and “experience with A/B testing tools.”
What they really mean is: can you prove your ideas work before spending the whole budget?
Marketers who test well get bigger budgets because they show ROI. They make fewer expensive mistakes. They build credibility with leadership. They move up faster than people who rely on intuition.
A Real Example
Your landing page gets 5,000 visitors per month. Your signup rate is 3%. That’s 150 signups monthly.
You think a shorter headline might work better. You test it. After two weeks, the new headline converts at 3.9%. That’s 30% better than your original.
You just added 45 signups per month without spending a dollar on more traffic. Multiply that across a year. Multiply it across multiple tests. Now you see why companies hire testers.
What You’ll Learn in This Series
Over the next four emails, you’ll learn:
How to set up control vs variation correctly
The 6-step process for running any test
Three different test types and when to use each
Five mistakes that waste traffic and time
Each email takes two minutes to read and teaches one practical concept.
━━━━━━━━━━━━━━━━━━━━━━
💡 QUICK WIN
Look at your most visited landing page right now. Write down the conversion rate. That number is your baseline. Everything you test tries to beat it.
━━━━━━━━━━━━━━━━━━━━━━
Coming up in Part 2:
Control vs Variation: The two-version setup that powers every test.
Reply with questions anytime.
– Atticus
P.S. Bookmark this calculator: CXL’s A/B Test Calculator. You’ll need it to determine how long to run tests. I’ll explain how to use it in Email 3.