Sampling Methods

Random Sampling Techniques

Random Sampling

Stratified Sampling - start with general population, divide into strata (groups) then apply simple random sampling to each strata

Cluster Sampling - unlike strata, each cluster should be representative of entire population of interest then apply simple random sampling to each cluster

Systematic Random Sampling - divide the count of entire population, N by count of desired sample size, n. For example, N=500 and n=50 then index k = 10. Choose kth element to build the sample.

Non-Random Sampling Techniques

Convenience Sampling - sample elements from the population that are most readily available.

Quota Sampling - a population is divided into groups (age, gender, location etc.). Random selection is better from groups but convenience sampling from the groups will lead to biased sampling.

Snowball Sampling - when the subject invites his or her friends to be interviewed or when interviewer asks if a subject can provide friends to be interviewed.