Yes, you can allocate only a certain percentage of your users to enter an experiment. For example you can configure that only 20% of your users should take part in an experiment.

It is also possible to define a custom JavaScript trigger method to further restrict who enters an experiment. For example you could activate the experiment only for users from a certain location. Read more about this in the developer docs for running an experiment.

Previous FAQ: We are already using an A/B Testing framework, can we keep using it?