This document discusses concepts related to measurement and sampling in field research. It defines key terms like population, element, sampling, sampling frame, census, survey, parameter, and statistic. The document explains that sampling involves selecting a subset of a population to study in order to make inferences about the larger population. It notes that samples must be representative of the population and discusses factors like sampling method, sample size, and sampling error that impact representativeness. The document also outlines the steps in the sampling process and lists some advantages of sampling like being faster and cheaper than studying the entire population.