Individual skill

experiment-design

Framework for running single-variable cold email experiments. Defines experiment types (list-only, copy-only, combined), confidence weighting, minimum sample sizes, and success criteria. Use when the user wants to improve a campaign, test a new list vs old one, or compare copy variants. Prevents the

skills/experiment-design/SKILL.md

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# Experiment Design

If you change your list, your copy, and your offer at the same time, you learn nothing. This skill forces you to isolate one variable per experiment so you actually learn what's working.

## Why this exists

Most cold email operators run "throw-everything" experiments. Campaign 1 gets a new list, new copy, and a new offer. It works better. They declare victory. But they can't tell you WHY — was it the list? The copy? The offer?

Then campaign 2 changes all three again. Regression. Nobody knows why.

This skill is the antidote: plan each experiment around ONE variable, keep everything else constant, and confidence-weight the results.

## The three experiment types