Randomization is a statistical method of randomly assigning participants to an experiment or control group, assuming each participant has a fair chance of being selected. Randomization helps to prevent bias, which may arise during subject selection, or accidental errors during and after the experiment. The simple randomization method divides the samples into two groups by flipping a coin or rolling a die. However, characteristics of the sample, such as gender, may affect the outcomes and act as a blocking variable. In such cases, block randomization is used, which separates the samples into blocks based on gender. Depending on the treatment group, individuals in each block are divided randomly into smaller groups. In stratified randomization, prognostic variables such as gender and body mass index are grouped and balanced. With these two covariates, six combinations or strata are possible. The individuals within these strata are then randomly assigned to a treatment or control group.