Randomization settings


  • You can enable randomization for your study in the study’s Settings tab, set "Randomization" to "Yes" using the available drop-down.
  • After saving the changes in the settings tab, open the randomization tab to define the randomization settings
  • Castor uses variable block randomization with optional stratification.
  • The randomization groups in this algorithm can also be weighted, but a one-to-one ratio is usually applied
  • When you begin randomizing, a block size will be determined randomly from this selection for each stratum.
  • As a researcher, you will not know the size of the blocks as they will be randomly generated.
  • We recommend consulting a statistician to ensure you are selecting the right block sizes.
  • First define the randomization groups by clicking the Add button
  • Add the name and select the weight
  • The first column defines the
  • In case of stratified randomization, add a field which will be used for stratification
  • Strata in Castor EDC are based on option group fields
  • Only dropdown and radio button fields can be used stratification 
  • You must first create this field in the form you want to stratify on
  • Select whether to stratify per institute 
  • This is only applicable for multi-center studies
  • Finally select the block sizes
  • Available block sizes are dependent on the number of groups and their assigned weight.
  • After going live it is no longer possible to change the Randomization settings.
  • You can add and test the randomization in your study before it goes live - it is possible to randomize your test record(s) to check if the randomization settings you have chosen are working correctly without concern over influencing the data you will collect later.
  • What is important to know is that this testing has to be done before the study is set to live
  • To test randomization, open the Records tab
  • The users in your study who will be doing the randomization need to have 'Randomize' rights
  • Add the data to a record, navigate to the Randomization and click the Randomize button
  • When you decide to start collecting real data, you will be able to reset your randomization. 
  • When  you set your study to live for the first time, you will be asked whether you want to reset the randomization. 
  • That means that the test records that were randomized will not influence the future randomization of the real record

Complete and Continue