Configuring experiment rollout

This skill answers: Who sees what variant?

Recommended approach: equal split + adjust rollout percentage

In most cases, experiments work best with an equal split. If you want to limit exposure to the test variant, adjust the rollout percentage instead.

Why equal splits are better:

• Equal splits maximize statistical power — each variant has the same sample size
• Equal splits balance traffic and thus reach significance faster
• Increasing user exposure throughout the experiment through increasing rollout is clean (changing split mid-experiment can cause users to switch variants, which is bad for user experience and data quality)

Always default to an equal split unless the user explicitly requests otherwise.

When an uneven split is required

Uneven splits combined with the default "Exclude multivariate users" handling can introduce bias.