Learning Objectives

By the end of this lesson, learners should be able to:

  • Explain non-probability sampling.
  • Distinguish among convenience, judgment, quota, and snowball sampling.
  • Evaluate when non-probability sampling is appropriate.

Meaning Of Non-Probability Sampling

In non-probability sampling, selection probabilities are unknown. Researchers choose respondents based on accessibility, judgment, quotas, or referrals.

These methods are common in exploratory research, pilot studies, and difficult-to-reach populations.

Convenience Sampling

Respondents are selected because they are easy to access.

Example

Surveying customers leaving a shopping mall.

Advantages

  • Fast,
  • Inexpensive,
  • Easy to implement.

Limitations

  • High risk of bias,
  • Poor representativeness.

Judgment (Purposive) Sampling

Researchers intentionally select participants with specific expertise or characteristics.

Example

Interviewing senior supply chain managers about global logistics disruptions.

Useful when expert knowledge is required.

Quota Sampling

Researchers select respondents until predetermined quotas are met.

Example

A survey requires:

  • 50% female respondents,
  • 50% male respondents.

Interviewers continue sampling until each quota is filled.

Quota sampling improves demographic balance but is not fully random.

Snowball Sampling

Existing participants recruit additional participants.

Example

Studying startup founders in emerging technology ecosystems.

Useful for hard-to-reach populations.

When To Use Non-Probability Sampling

  • Exploratory research,
  • Concept testing,
  • Pilot surveys,
  • Expert interviews,
  • Rare populations,
  • Qualitative research.

International Example

A consulting firm studying cybersecurity practices interviews recognized experts in United States, Germany, Israel, Singapore, and Japan using purposive sampling.

Bias Risks

Non-probability samples may overrepresent accessible or cooperative individuals. Researchers should avoid making strong population-wide claims from such samples.

Learning Materials / Reference Materials

  • Saunders et al. Research Methods for Business Students.
  • ESOMAR Qualitative Research Guidelines.

Lesson Summary

Non-probability sampling is useful when probability sampling is impractical, but researchers must recognize its limitations and avoid overstating conclusions.

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