At a high level, sampling can be divided into probability sampling and non-probability sampling. Probability sampling means that each unit in the population has some probability of being selected. The most common types of probability sampling include:

**Simple Random Sampling**: Each unit of the population has an equal probability of being chosen. The actual sampling is often done through the use of a random number generator. For example, if the population is all students at a university, a simple random sample could be formed by choosing a random list of IDs of all enrolled students.