This video looks two methods of trying to get a better balance between two groups namely blocked randomization and stratified randomization. Blocked randomisation tries to ensure that approximately the same number of patients are randomized to each group, and stratified randomization tries to ensure that the proportion of important predictive characteristics between patients are balanced between groups.

This video introduces the three main concepts in Randomized Trials, the ABC: Allocation at random, Blindness and Control

This video looks at a different form of randomization, minimization. This method can be more efficient than stratification at ensuring balance in important predictive characteristics, but is not true randomization.

This video looks at randomization when the patients are grouped into clusters. Since the clusters tend to be relatively few, getting balance is generally more important than with simple randomization.

This video introduces the concept of randomization of treatments to patients using playing cards. It describes simple randomisation, which is the purest form of randomization