> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kameleoon.com/llms.txt
> Use this file to discover all available pages before exploring further.
# CUPED
> Learn how Controlled-experiment Using Pre-Experiment Data (CUPED) accelerates reliable results by leveraging existing visitor data.
Controlled-experiment Using Pre-Experiment Data (CUPED) uses data from existing visitors to accelerate reliable experimentation and personalization results.
## Key benefits
Use CUPED to make data-driven decisions faster and with more confidence. CUPED provides better estimates for variation effects and reduces the risk of false-positive results for tests with limited data.
## When to use CUPED
CUPED is most effective when:
* You've collected goal data for at least two weeks before the experiment launch.
* A correlation exists between goal conversions before and during the experiment.
Consider your experiment goals before enabling CUPED. Activate CUPED for the main metrics of your site, such as transactions.
## Enable CUPED
To enable CUPED:
1. Open the experiment and click the **Data** tab in the sidebar.
2. Under **Advanced settings**, click the **toggle** next to **CUPED**.
3. Click the **dropdown menu**, then select the goals for which you want to enable CUPED.
4. Click **Apply**.
CUPED only works with the Frequentist statistical method. It doesn't work with Sequential testing or Bayesian.
Data loading might take longer than with the classic algorithm. Limit CUPED to your key goals to maintain performance.
The page data changes based on the selected goals. If you select your primary goal, the main results block displays CUPED-adjusted data labeled **CUPED enabled**.
Similarly, the results tables for each goal update based on the enabled CUPED settings.
The results columns display three primary differences:
* **Conversion rate** becomes **Conversion rate adjusted**
* **Improvement rate** becomes **Improvement rate adjusted**
* **Reliability** becomes **Reliability adjusted**
Kameleoon only supports filter-based breakdowns on results data when CUPED is disabled. Clicking **Breakdown** on a table prompts you to confirm disabling CUPED, and you can reactivate CUPED after you remove the breakdown filter.
CUPED effectiveness increases over time. As you use Kameleoon, the algorithm leverages more experiment data to improve accuracy.
## Further reading
For more information on CUPED, read the [Kameleoon statistical paper](https://storage.googleapis.com/kameleoon-storage-documentation/user-manual/pdf/statistics-at-kameleoon.pdf).