ABSTRACT
This chapter covers the principles guiding the selection of a sample. It focuses on the basic sampling and data collection strategies. The chapter discusses four common probability sampling designs: simple random sampling, systematic sampling, stratified sampling, and cluster sampling. Systematic sampling may be the only feasible way to get a probability sample of a population of unknown size, such as people attending a community festival. Nonprobability samples cannot produce estimates with mathematical precision, because the sample members do not have a known chance of being selected. Availability or convenience sampling is done when cases are selected because they are easily accessed. Quota sampling, often used in market research, is less common in social science studies. Sampling problems are particularly challenging for Internet surveys. Telephone surveys have been especially valuable in collecting data from the general public. People unfamiliar with sampling theory often assume that a major factor determining sample size is the size of the entire population.
