Randomization is a procedure of randomly assigning study participants to different groups (arms), such as the treatment group or the control group receiving a placebo or standard treatment. Well-randomized trials can improve the external validity of a study, making its findings more generalizable to the broader population.
Definitions
ICH E6(R2)
- 1.48 Randomization:
- The process of assigning trial subjects to treatment or control groups using an element of chance to determine the assignments in order to reduce bias [1].
Purpose of randomization
Randomization is a requirement for experimental studies to control bias and confounding variables:
- random allocation between study arms can reduce selection bias and ensure that the groups are comparable at the start of the trial.
- randomization helps distribute confounding variables evenly between study groups.
By minimizing bias and balancing confounding variables, randomization enhances the internal validity of the study.
Methods of randomization
Simple randomization
The simplest method, where every participant has an equal chance of being assigned to any group, often done using random number generators. Due to the nature of random distribution, this method may result in unequal experimental and control group sizes or an uneven distribution of potential confounding variables.
Block randomization
Participants are assigned to blocks within which the experimental and control groups are distributed evenly and randomly. The block size should be concealed to avoid accidental bias.
Stratified randomization
Participants are first divided into strata based on certain characteristics (e.g., age, gender) and then randomized within each stratum to ensure balance across these characteristics.
Minimisation
An adaptive method of assigning participants to different groups to ensure balance across several predefined variables [2]. Unlike traditional randomization, minimisation considers the characteristics of participants already assigned to the trial groups and allocates new participants in a way that minimizes imbalance between the groups.
Cluster Randomization
Predefined groups of subjects (e.g., individual clinics) are randomized rather than individual participants.
See also
Another relevant pages
Links to this page
- Phase II clinical trials (← links)
- Placebo (← links)
- Clinical study (← links)
- Subject identification code (← links)
References
- ↑ ICH, 2016, Integrated Addendum to ICH E6(R1): Guideline for Good Clinical Practice E6(R2), https://database.ich.org/sites/default/files/E6_R2_Addendum.pdf Accessed Sep 2023
- ↑ Taves D.R., 1974, Minimization: a new method of assigning patients to treatment and control groups. Clinical pharmacology and therapeutics, 15(5), 443–453. https://doi.org/10.1002/cpt1974155443 Accessed May 2024
External links
- Quantics Biostatistics, 2023, Randomisation for Clinical Trials: A Guide https://www.quantics.co.uk/blog/randomisation-for-clinical-trials-a-guide/ Accessed May 2024
- Berger, Vance W et al. A roadmap to using randomization in clinical trials. BMC medical research methodology vol. 21,1 168. 16 Aug. 2021, doi:10.1186/s12874-021-01303-z https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8366748/#CR9 Accessed Jun 2024
- Lim, Chi-Yeon, and Junyong In. Randomization in clinical studies. Korean journal of anesthesiology vol. 72,3 (2019): 221-232. doi:10.4097/kja.19049 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6547231/ Accessed Jun 2024
- Suresh, Kp. An overview of randomization techniques: An unbiased assessment of outcome in clinical research. Journal of human reproductive sciences vol. 4,1 (2011): 8-11. doi:10.4103/0974-1208.82352 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3136079/ Accessed Jun 2024
- Kang, Minsoo et al. Issues in outcomes research: an overview of randomization techniques for clinical trials. Journal of athletic training vol. 43,2 (2008): 215-21. doi:10.4085/1062-6050-43.2.215 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267325/ Accessed Jun 2024