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simple randomization

Simple randomization/Complete randomization, also known as group design, is a method of controlling error variation through randomization. It is believed that after randomization, the variation between samples is randomly distributed at various processing levels, so that the differences in experimental results can be attributed to the influence of different treatments. This design assumes that randomization can balance the differences between subjects, but in reality, individual differences are often included in experimental results. If we can exclude these individual differences, the experimental results will be more accurate.

The simple randomization method is easy to use and easy to operate when computer technology is not advanced. With the popularization and application of Internet technology, simple randomization has been less used in clinical research due to its shortcomings.

simple

block randomization

Block randomization, also known as compatibility design or compatibility group design, usually involves dividing the subjects (samples) into several groups (compatibility groups) based on their properties (such as age, gender, blood pressure, weight, and other non experimental factors) that are the same or similar. The subjects (samples) in each group are randomly assigned to different treatment groups.[1]

Random block design is a design method that uses block methods to separate variations caused by irrelevant variables. The method of balancing the experimental group and the control group in the same group is actually an extended form of paired design. The key point is to achieve homogeneity within the group as much as possible, so that the differences in experimental results can be better attributed to the influence of different treatments[2]. The disadvantage of random block design is that it requires the number of subjects in the block to be equal to the number of treatments, and if there are missing data in the experimental results, statistical analysis can be difficult [3].

stratified randomization

Stratified randomization, compared to simple block randomization. The simple block randomization method is aimed at grouping all subjects, which can only ensure that the subjects are divided into two groups according to the overall sample size, and cannot guarantee that each group has similar physiological factors such as gender, age, etc. (generally no more than three). The grouping randomization method can achieve a balance between the physiological characteristics of two groups of subjects. The specific operation is to first group or stratify all participants according to specified factors, and then perform block randomization for each group. The group randomization method may be more cumbersome compared to the general block randomization method, but it balances the physiological characteristics of the two groups and avoids errors caused by non experimental factors.