Statistics
The maths behind whether a test actually told you anything. Hypothesis design, sample size, power, MDE, and the threats to validity that quietly invalidate results.
Learn CRO & Growth: Notes by Alex
Working notes on CRO, experimentation, and growth engineering. Written to be shared with a client or teammate in one click.
What’s in here
Section titled “What’s in here”Experimentation
Designing, running, and reading A/B tests without lying to yourself. Foundations, test design, analysis, and the operational layer that turns one-off tests into a programme.
Conversion psychology
The persuasion frameworks, cognitive biases, and decision-making models behind why CRO tactics work (and why some backfire).
Marketing concepts
Where CRO sits in the broader commercial picture. Offers, funnels, attribution, LTV, and the strategic context that bounds what testing can achieve.
Growth engineering
The technical work that compounds across every experiment. Feature flags, instrumentation, personalisation, and the infrastructure that turns ideas into shipped variants.
About these notes
Section titled “About these notes”These are based on notes I’ve accumulated over years working in CRO and growth - originally fragmented in Obsidian, now polished into something I’d actually share (thanks Claude). I put them together for two reasons.
First, I wanted a clean reference I could send to a client or teammate when a concept came up. Pointing at a link is faster than re-explaining what holdouts are or why peeking inflates the false-positive rate, and shared references are easier to argue against than my own off-the-cuff explanations.
Second, writing things up properly is the fastest way I know to surface gaps in my own thinking. The act of explaining a concept publicly forces a precision that private notes never quite get to.
About me
Section titled “About me”I’m Alex. I’ve spent 8+ years helping brands like Ford, De Beers, and Hasbro work better - running lean CRO programmes, leading UX, building storefronts from the ground up, and designing content structure for growth. These notes are what fell out of that work, written up properly.