Randomization means that each observation unit in the group has an equal chance to be selected into the sample and an equal chance to be grouped.
The purpose of random grouping is to make the experimental group and the control group comparable through random balanced interference factors and avoid bias caused by subjective arrangement. Generally used in randomized controlled studies (RCT), yes, you are right, that is, R.
The process of randomization is generally realized by coin toss, lottery, random envelope and center randomization. At present, random envelope and central randomization are widely used. The method of central randomization through telephone, computer and mobile app will be the trend of future randomization, because central randomization can prevent researchers from destroying randomization in some subjective ways.
In addition, random grouping ensures that subjects have equal opportunities to be grouped, but it does not guarantee that the randomized result will be the most ideal equilibrium, which may lead to the opportunistic imbalance of baseline characteristics. Therefore, in order to ensure the ideal balance of the factors that have great influence on the research results in the random grouping results, stratified randomization and block randomization can also be carried out.
For example, a certain treatment may have different effects on different sexes. In order to prevent the imbalance of gender distribution between groups after random grouping, we can stratify by gender in the case of random design center, so that the gender ratio in each group is almost equal.
: random sampling
Random sampling, according to the principle of randomness, ensures that every object in the crowd has a known probability to be selected as the research object, in order to ensure the representativeness of the sample. Commonly used random sampling methods mainly include pure random sampling, stratified sampling, systematic sampling, cluster sampling and multi-stage sampling.
Random sampling is widely used in observational studies, such as cross-sectional studies, cohort studies and case-control studies. Generally, random sampling needs to make a sampling plan and determine the sampling frame first, and then choose by lottery, random number table, computer-generated pseudo-random number and other methods.
The process of generating random numbers and determining drawing numbers can be realized by Excel, SPSS, SAS and other programs, which is relatively simple.