Generate randomization schemes for clinical trials and experiments with downloadable assignment lists. This calculator supports simple randomization, block randomization, and stratified randomization methods to ensure proper allocation of participants to treatment groups.
Ready to randomize your study participants? to see how block randomization works, or configure your own randomization scheme.
Randomization is a fundamental principle in experimental design that helps ensure unbiased allocation of participants to treatment groups. It minimizes selection bias and balances known and unknown confounding variables across groups.
Each participant has an equal probability of being assigned to any group. While straightforward, this method can result in unequal group sizes, especially with small sample sizes.
Best for:Large studies (n > 200) where slight imbalances are acceptable.
Participants are randomized in blocks to ensure equal group sizes at regular intervals. For example, with 2 groups and block size of 4, every 4 participants will have 2 assigned to each group.
Variable block sizes (e.g., 4, 6, 8) add unpredictability and prevent selection bias by making it harder to predict assignments near the end of a block.
Best for: Small to medium studies where balanced group sizes are critical.
Randomization is performed separately within each stratum (e.g., by site, age group, or disease severity). This ensures balance across important prognostic factors.
Best for: Multi-center trials or studies with known important baseline characteristics.
