---
title: "What is Holdout group? | Chargezen"
description: "A holdout group is a random slice of an audience that deliberately gets no message, so you can measure how much the message really changed behavior."
url: "https://chargezen.com/glossary/holdout-group"
lang: "en"
---

Canonical URL: https://chargezen.com/glossary/holdout-group

# Holdout group

Holdout group (control group)

Email Marketing

A holdout group is a random slice of an audience that deliberately gets no message, so you can measure how much the message really changed behavior.

## What is Holdout group?

An A/B test compares message against message. A holdout compares message against **no message**. Some of the people who buy after an email would have bought anyway; the holdout shows how many. **How it works:** randomly hold back, say, 10% of a flow or campaign audience, then compare their purchase rate with everyone who got the message. The difference is the **incremental lift**. **In SmartyTap,** A/B tests compare versions and don't create a no-message group automatically. You can approximate one by excluding a segment you set aside from a campaign and comparing its orders with the people who got the message.

## Example

A win-back flow goes to 90% of lapsed customers; 10% get nothing. After 30 days, 6% of the messaged group and 4% of the holdout reordered: a 2-point lift.

## Why Holdout group Matters

Attribution counts every order after a click; a holdout tells you which orders the message actually caused.

## Holdout group FAQ

How big should a holdout group be?

Often 5 to 20% of the audience, large enough to show a difference in orders.

Isn't holding people back lost revenue?

A little, for a while. It's the price of knowing whether a message earns more than it costs.

## Explore More Terms

Browse our complete glossary of e-commerce and subscription terms.

[View Full Glossary](https://chargezen.com/glossary)