While your study is under development, i.e. before going live for the first time, you can set up, test, and modify the randomization settings. When going live for the first time, you will be offered to reset the randomization, thus effectively clearing up all test randomization data.

Once the study has been live, even if later changed back to 'not live', randomization settings can no longer be changed within the study. Depending on the type of change that is needed, Castor Support may be able to offer assistance.

Randomization Settings: When a study has been live, the randomization settings cannot be changed by any study user. This is because changing the randomization settings has significant statistical implications and should thus be performed with extreme caution. For assistance with changing the randomization settings after going live, you must contact Castor Support. 

Generally, changes are safe to do if no randomization was previously set up in the study or if only test participants were randomized. However, if you have already started randomization of real subjects, making changes has significant statistical implications and therefore we require a confirmation from a statistician that this change is necessary and acceptable for the study. We will also require a waiver to be signed, before any changes are made.

Randomization Allocation: If a problem occurs with randomization, for example, a user has randomized a participant that shouldn't have been randomized, it is possible to request via Castor Support to remove the randomization from the system. 

This is only possible in certain circumstances that will be evaluated on a case-by-case basis. For example, if the participant is the last participant that was randomized, it would be possible to remove the allocation. 

A waiver must be signed before changes are made. A fee might be requested for this type of change as it requires intervention from our development team.