Individuals are chosen as opportunities arise
Oppurtunity sampling
Individuals are chosen through random procedure
Simple random sampling
if populations are divided into representative subgroups, then you take samples from a few of these subgroups.
Cluster sampling
If the parent population is divided into distinct subgroups (strata) that clearly represent underlying features, then these strata may affect the outcome being investigated. In which case, one can sample based on strata so all strata are to some extent represented. We can either sample equal amounts of people from each strata, or we can sample strata based upon their prominence in the complete population
Stratified sampling
We require a set number of people per strata, with no reason why we are sampling in such a way
quota sampling
Volunteers are sampled
Self selected sampling
any identifiable method of sampling
Systematic sampling