Simple Random Sampling is a method of choosing samples in which all themembers of the population are given an equal chance of being selected.

Systematic Random Sampling is a method where the population is divided into different strata (groups), and then the samplingfollows. Age, gender, and educational qualifications are some possible criteriaused to divide a population into strata.  

Convenience Sampling involves choosingrespondents at the convenience of the

            researcher. It is also called accidental or incidental sampling.  

Volunteer Sampling involves people whoself-select into the survey. Often, these

            folks have a strong interest in themain topic of the survey

Purposive Sampling does not give a specific set of samples, similar to snow

 expanding widely or rolling rapidly. This is true for a study involving unspecified  group ofpeople. Dealing with varied groups  ofpeople such as street children, drug dependents, gang members, informal settlers, street vendors, and thelike is possible  in this kind ofnon-probability sampling.