What randomization algorithms are available?

You can use simple or stratified randomization. You can create blocks in the list and assign them either dynamically or statically to sites, countries, or regions.

For stratified randomization, subjects are grouped during the randomization event to maintain a balance of treatment arms. For both simple and stratified randomization, you can create blocks in the list and assign them to sites, countries, or regions.

Tip:

You have two options for grouping subjects: Either choose a stratified randomization design and then create stratum groups, or use demography cohorts. Demography cohorts offer more flexibility for controlling your enrollment because they let you set limits on population groups and stop and start enrollment for a group with just a few clicks.

How the sequence number is used with an existing randomization

If you use this option, you must already have a randomization algorithm in place. The sequence number acts as additional layer of shuffle to the existing randomization list. For example, if the randomization algorithm assigns numbers in a list, such as 1001, 1042, 1203, the sequence number option will reorganize this list into a less predictable format, such as 4, 50, 993. This is achieved by sorting the original list based on the lowest sequence number assigned to each item.

The sequence number is compatible with any randomization type, except for minimization.

If you leave the sequence number field blank, Oracle Clinical One Platform will default to the original randomization order, and no additional shuffling will occur.

The sequence number option is useful when a study is being run for a very small set of subjects, as it adds an additional layer of blindness by making the randomization numbers being less predictable.

You choose from the following algorithms for randomizing subjects.

Type of randomization algorithm	When a subject is randomized	How blocks of randomization numbers are assigned	When a block is exhausted by a stratum group at the country	Additional details
Central randomization	Oracle Clinical One Platform selects the next treatment arm in a central randomization list.	Not applicable.	Not applicable.	Not applicable.
Central Stratified randomization	Not applicable.	Not applicable.	Oracle Clinical One Platform selects the next treatment arm in a central randomization list based on strata.	This type of randomization is useful when you want to balance treatment arms within stratum groups.
Country Blocked Dynamic randomization	Oracle Clinical One Platform selects the next treatment arm from the block assigned to the site's country.	Oracle Clinical One Platform dynamically allocates blocks of randomization numbers to countries.	The next available block is allocated to the country.	This type of randomization helps you balance treatment arms within a country while minimizing gaps between blocks.
Country Blocked Dynamic Stratified randomization	Oracle Clinical One Platform selects the next treatment arm from the block assigned to the country based on strata.	Oracle Clinical One Platform dynamically allocates blocks of randomization numbers to stratum groups at each country.	The next available block is allocated to the stratum group at the country.	This type of randomization is useful when you want to balance treatment arms within the stratum groups in each country.
Country Blocked Fixed Stratified randomization	Oracle Clinical One Platform selects the next treatment arm from the block assigned to the country based on strata.	You assign blocks to each country when you create the randomization list.	Oracle Clinical One Platform selects the next treatment arm in the next block that is allocated to the site's country. If all blocks allocated to a country are exhausted, a randomization failure occurs.	This type of randomization is useful when you want to balance treatment arms within a country. You must pre-allocate blocks of randomization numbers to countries when you create the randomization list, and if all blocks are exhausted, a randomization failure occurs. Additionally, gaps between blocks can occur when sites don't use randomization numbers as expected.
Country Blocked Fixed randomization	Oracle Clinical One Platform selects the next treatment arm from a block assigned to the site's country.	You assign blocks to each country when you create the randomization list.	Oracle Clinical One Platform selects the next treatment arm in the next block that is allocated to the site's country. If all blocks allocated to a country are exhausted, a randomization failure occurs.	This type of randomization helps you balance treatment arms within a country. You must pre-allocate blocks of randomization numbers to countries when you create the randomization list, and if all blocks are exhausted, a randomization failure occurs. Additionally, gaps between blocks can occur when sites don't use randomization numbers as expected.
Minimization	Oracle Clinical One Platform selects a treatment arm using equal randomization.	Blocks are not assigned in the randomization list.	This type of randomization helps you balance subjects with different stratum factors and can be particularly useful within smaller cohorts.	Minimization is deterministic which means that some blinded users are at risk of predicting which minimization stratum group a subject is enrolled in. Additionally, it is a type of randomization that is not often used due to its complexity.
Site Blocked Dynamic randomization	Oracle Clinical One Platform selects the next treatment arm from the block assigned to the site.	Oracle Clinical One Platform dynamically allocates blocks of randomization numbers to sites.	The next available block is allocated to the site.	This type of randomization helps you balance treatment arms within a site while minimizing gaps between blocks.
Site Blocked Dynamic Stratified randomization	Oracle Clinical One Platform selects the next treatment arm from the block assigned to the site.	Oracle Clinical One Platformdynamically allocates blocks of randomization numbers to stratum groups at each site.	The next available block is allocated to the stratum group at the site.	This type of randomization is useful when you want to balance treatment arms within the stratum groups in each site.
Site Blocked Fixed randomization	Oracle Clinical One Platform selects the next treatment arm from a block assigned to the site.	You assign blocks to each site when you create the randomization list.	Oracle Clinical One Platform selects the next treatment arm in the next block that is allocated to the site. If all blocks allocated to a site are exhausted, a randomization failure occurs.	This type of randomization helps you balance treatment arms within a site. You must pre-allocate blocks of randomization numbers to sites when you create the randomization list, and if all blocks are exhausted, a randomization failure occurs. Additionally, gaps between blocks can occur when sites don't use randomization numbers as expected.
Region Blocked Dynamic randomization	Oracle Clinical One Platform selects the next treatment arm from the block assigned to the site's region.	Oracle Clinical One Platform dynamically allocates blocks of randomization numbers to regions.	The next available block is allocated to the region.	This type of randomization helps you balance treatment arms within a region while minimizing gaps between blocks.
Region Blocked Fixed randomization	Oracle Clinical One Platform selects the next treatment arm from a block assigned to the site's region.	You assign blocks to each region when you create the randomization list.	Oracle Clinical One Platform selects the next treatment arm in the next block that is allocated to the site's region. If all blocks allocated to a region are exhausted, a randomization failure occurs.	This type of randomization helps you balance treatment arms within a region. You must pre-allocate blocks of randomization numbers to regions when you create the randomization list, and if all blocks are exhausted, a randomization failure occurs. Additionally, gaps between blocks can occur when regions don't use randomization numbers as expected.
Region Blocked Dynamic Stratified randomization	Oracle Clinical One Platform selects the next treatment arm from the block assigned to the region.	Oracle Clinical One Platform dynamically allocates blocks of randomization numbers to stratum groups at each region.	The next available block is allocated to the stratum group at the region.	This type of randomization is useful when you want to balance treatment arms within the stratum groups in each region.

Parent topic: Randomization FAQs (for study designers)