The characteristics of simple random sampling are: the probability of each sample unit being extracted is equal, and each unit of the sample is completely independent, and there is no certain correlation and exclusion between them.
Its greatest advantage is that when inferring a population from sample data, it can objectively measure the reliability of the inferred value in a probabilistic way, thus making this inference based on science. Because of this, random sampling is widely used in social investigation and social research. Commonly used random sampling methods mainly include pure random sampling, stratified sampling, systematic sampling, cluster sampling and multi-stage sampling.
Extended data
Simple random sampling design: a sampling method that makes all sampling units in the population have equal probability of being drawn into the sample. Common simple random sampling methods include drawing lots or using random numbers.
Stratified random sampling design: If the population contains some non-overlapping mutually exclusive parts (called layers), it is caused by factors such as age, gender, race or geographical location. If there are such layers, the stratified random sampling design will take samples from each layer.
The samples obtained in this way are more representative than those obtained by simple random sampling, thus making the inference more effective. If the proportion of the random sample size of each layer in the sample is equal to the proportion of the elements of this layer in the population, it is called proportional stratified random sampling, otherwise it is called non-proportional stratified random sampling.
Systematic random sampling design: If the sampling framework is very large, systematic random sampling is usually adopted. In systematic random sampling, every k elements in the sampling frame are selected as sample elements, and the first extracted element (called initial element) is randomly selected from the first k elements. If there is obvious periodicity or cyclicity in the sampling box, systematic random sampling should be avoided.