06.4.2 · Skill in Experiment design
Control groups
A comparison group that does not get the change.
A control group shows what would have happened without the change. Without it, seasonal effects, marketing pushes and bugs look like results. Holdout groups extend the idea over longer periods.
Resources
1- docsStart hereHoldout experiments ↗GrowthBook docs · 2026 · 10 min
How to keep a group of users without new features to measure long-term impact, and the trade-offs of doing so.
Tools
1- ToolOpen sourceGrowthBook
Open-source feature flags and A/B testing that analyzes results from your own data warehouse.