---
title: Choose metrics in Feature Experimentation
slug: feature-experimentation/docs/choose-metrics-in-feature-experimentation
docTags: 
createdAt: 2026-08-05T20:39:56.000Z
---

- Optimizely Feature Experimentation

[Metrics](docId\:QMhSl6-5c54bbhHlZwMcp) are a quantitative measure of the success of your experiment. They tell you whether the variations in an experiment are winning, losing, or inconclusive based on changes in visitor behavior in response to your experiment.

For example, suppose your site has an Add-to-Cart button. You would use an **event** to track every time the button is clicked. You would use a **metric** to measure the percentage of users who added to the cart at least once or the average number of items added per user.

## Choose primary and secondary metrics

The primary metric is the one Optimizely Feature Experimentation uses to determine a statistically significant winning or losing variation. It is the most important goal of the experiment, and it decides whether your hypothesis is proven or disproven. In Optimizely Feature Experimentation, the primary metric achieves statistical significance at full speed, regardless of any other goals or events added. Additional metrics are called secondary or monitoring metrics. Select secondary metrics that give you insights into long-term success. See [Primary metrics, secondary metrics, and monitoring goals](docId\:oWMQ0BWo1DoM2WWKINZSP) for information.

Identifying the correct metric is a huge factor in determining whether your experiment has statistically significant results. See the following support articles:

- [Types of metrics and when to use them](docId:8gpGLNz8DTMSwpnQ_giQj).
- [Build a goal tree to improve metrics that matter with your optimization program](docId\:k_80tqMJv2Kdh1yU1jjyX).
- [Metrics do not track correctly](docId\:Rv7KCRArlJGavaNIZj2SV).

## How metrics are calculated

Optimizely Feature Experimentation creates metrics by aggregating [events](docId\:puGm9z4XkEG5PDkyaNmlA) over time. Directly track actions like clicks, pageviews, form submissions, purchases, and scroll depth. After you [create an event](docId\:v2goO-UxyIA4AtTSR-h-9) and add it to an experiment, you decide how it is displayed as a metric.

## Add metrics to experiments

Every Optimizely Feature Experimentation experiment needs at least one metric. You can add or modify metrics at any time.

- For details on adding metrics to experiments, see [Run A/B tests](docId:8pnfCv-sR37goLcxTtCPv) or [Run a multi-armed bandit optimization](docId:9Tu731hmFrs5KHzlIsT7N).
- To create a metric, see [Create a metric in Optimizely with the metric builder](docId\:cphstZe3xKhsY7WsnnLZK).
- To view the metrics attached to your experiment, see the [Experimentation Results page](docId:_K6n7h_MZ8b0xn6yWPrrq).