---
title: Take action now: SRM detected experiment health
slug: experimentation-strategy/docs/take-action-now-srm-detected-experiment-health
docTags: 
createdAt: 2026-08-05T20:33:23.916Z
---

- Optimizely Web Experimentation
- Optimizely Performance Edge
- Optimizely Feature Experimentation
- Optimizely Full Stack (Legacy)

A **SRM detected **experiment health on the [Optimizely Experiment Results page](docId\:mrUblIuNVOZc1dvjWdsbw) means that your A/B test has failed a traffic imbalance check. The patterns of visitor assignments to variations in your experiment must be investigated to identify the problems. 

![](https://api.archbee.com/api/optimize/BrbvVORKJ5iIeSMZye5kI/IqoBFkwMm0GmxGYJBFhUa-20260720-144750.png)

When you launch a[ Stats Engine](docId\:e7e-S6BollFwcP1RX9YS_) A/B test, Optimizely Experimentation's [automatic sample ratio mismatch (SRM) detection](https://www.optimizely.com/insights/blog/introducing-optimizelys-automatic-sample-ratio-mismatch-detection/) runs in the background. This algorithm identifies imbalances in visitor traffic to an experiment's variations, so you know of potential problems early.

An experiment displaying a **SRM detected** health status indicates that Optimizely Experimentation's automatic SRM detection algorithm identified a significant imbalance. The algorithm checks solely on the *first decisions*, which includes just the first decision (impression) for a visitor either within a variation (for visitor-scoped metrics) or session (for session-scoped metrics). See [How Optimizely Experimentation counts conversions](docId\:onBazDzYYz526tL9aQF0s).

Identifying an SRM among these first decisions signals a critical imbalance. It indicates an issue in how visitors are initially bucketed, which can impact the accuracy of experiment results.

:::hint{type="warning"}
**Important**

Because Optimizely's SRM detection can uncover a potential SRM earlier than a traditional chi-squared test, it is important to examine the data on the specific date when SRM is identified.
:::

## SRM detected health status

A **SRM detected** experiment health status is statistically significant, and there is evidence of consistent and undeniable underlying assignment bias. The experiment should be paused immediately to investigate the issue.

See [Imbalance detected: What to do if Optimizely's automatic SRM detection alerts you to an imbalance in your Stats Engine A/B test](docId:2VGHBuvjNAJJnkir0LDTz). 

## Why an SRM occurred

For a list of possible reasons, see [Possible causes for traffic imbalances](docId\:N_ilK-GbTBHGj00qGjVri).