1. Simple random sampling: a certain number of samples are randomly selected from all college students to ensure that everyone has an equal opportunity to be selected. This method is suitable for small sample size and small difference between samples.

2. Stratified sampling: All college students are stratified according to certain characteristics (such as gender, age, major, etc.). ), and then a simple random sampling at each level. This method can not only ensure the representativeness of samples, but also take into account the differences between different levels.