---
title: What is Incrementality?
url: https://markin.ai/glossary/incrementality
category: Experimentation and causality
aliases: Incremental lift, Causal lift
---

# Incrementality

> Incrementality is the portion of an outcome that would not have happened without the action. It is measured against a randomised control, not inferred from attribution, and it is routinely far smaller than the numbers a last-touch report shows.

## How it is calculated

```
Incremental revenue = Treated group revenue - Holdout revenue (per customer, scaled)
```

Report a confidence interval. A point estimate without one cannot support a budget decision.

## Why it matters for ARPU

Incremental ARPU is the only version of the number that survives scrutiny, and it is the currency Markin reports in.

## Related terms

- [Holdout group](https://markin.ai/glossary/holdout-group), A holdout is a randomly selected set of customers deliberately excluded from an action, kept as the counterfactual.
- [Uplift model](https://markin.ai/glossary/uplift-model), An uplift model estimates the change in outcome caused by treating a customer, rather than the outcome itself.
- [Experiment](https://markin.ai/glossary/experiment), An experiment is a controlled release of a candidate action against a randomised holdout, sized in advance so the result can distinguish a real effect from noise.
- [A/B test](https://markin.ai/glossary/ab-test), An A/B test randomly assigns customers to two or more variants and compares a pre-declared metric between them.

## Go deeper

- [Cross-sell without cannibalization](https://markin.ai/blog/cross-sell-without-cannibalization), Incrementality applied to expansion.
- [Markin product](https://markin.ai/product), Causal read-out in the loop.

Source: https://markin.ai/glossary/incrementality