Learning Objectives

  1. Identify the circumstances that make sampling unnecessary and the reason they are rare.
  2. Identify the relation among the desired sample, the obtained sample, the sampling frame, and the sample quality.
  3. Define and distinguish between probability and nonprobability sampling and both techniques’ relationship to sample generalizability.
  4. Define the major types of probability sampling and indicate when each is preferred.
  5. Explain when nonprobability sampling methods may be preferred.
  6. Describe the concept of sampling error and explain how its size is affected by the heterogeneity of the population and the fraction of population included in the sample.