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COMM 301: Empirical Research in Communication

COMM 301: Empirical Research in Communication. Kwan M Lee Lect6_1. Sampling Non-probability sampling. Things to know by the end of the lecture How is non-probability sampling different from probability sampling Why and when do we use non-probability sampling?

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COMM 301: Empirical Research in Communication

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  1. COMM 301:Empirical Research in Communication Kwan M Lee Lect6_1

  2. Sampling Non-probability sampling • Things to know by the end of the lecture • How is non-probability sampling different from probability sampling • Why and when do we use non-probability sampling? • What are the non-probability sampling techniques?

  3. Sampling Non-probability sampling • Non-probability sampling • do not rely on mathematical rules to select the sample • cannot estimate sampling error • So why do we use non-probability sampling? • Sometimes, using probability sampling cannot get a meaningful sample (illustrated below) • Sometimes, it costs less effort, time, resources • Non-probability can supplement probability sampling • Cf. What is the main advantage of probability sampling over non-probability sampling? • Calculation of sampling errors  increase generalizability

  4. Sampling Non-probability sampling • Non-probability sampling methods • convenience • volunteer • purposive • quota • network

  5. Sampling Non-probability sampling • Convenience sampling • select elements because they are accessible • no use of mathematical rules • e.g. surveys conducted in the mall

  6. Sampling Non-probability sampling • Volunteer sampling • select based on agreeing to participate • for human subjects, especially minors, this is a key ethical principle • are volunteers different from non-volunteers?

  7. Sampling Non-probability sampling • Purposive sampling • Key advantage of purposive sampling over probability sampling • Make it possible to select samples with very rare and unique characteristics (which we plan to study). • e.g. study CEO communication in bankruptcies of large firms • Montgomery Wards, K-Mart, Enron • common in case studies

  8. Sampling Non-probability sampling • Quota sampling • similar to stratified sampling • but without use of mathematics-based random selection • use of non-probability methods (convenience, volunteer, etc.)

  9. Sampling Non-probability sampling • Network sampling • select members based on other sample members identifying • used in qualitative research • e.g. in-depth interviews in organizations

  10. Sampling Non-probability sampling • In general, when using non-probability sampling, need to consider carefully issues of representativeness

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