Sampling Strategies

Theoretical sampling (Glaser)

After initial coding, theoretical sampling seeks data to elaborate properties, dimensions, conditions, and consequences of emerging categories. You sample for analytic gaps, not demographic quotas (unless demographics are theoretically relevant). The question is: “What data do I need next to develop this category?”

Snowball and chain referral sampling

Use when populations are hard to reach or trust is network-based. Mitigate bias from seed participants by using multiple entry points and monitoring whose voices dominate. Document referral chains in audit materials.

Maximum variation vs typical case

Maximum variation guards against provincial theory; typical case helps communicate mundane patterning. In GT, these are tools in service of emergent categories—choose based on what the evolving theory demands.

Convenience sampling (with caveats)

Convenience sampling is acceptable only when limitations are transparent and you take compensatory steps (prolonged engagement, triangulation, negative case search). Never dress convenience up as theoretical sampling without analytic justification.

Sample size in qualitative research

“How many?” depends on study scope, data richness, and saturation. A focused GT project may achieve workable saturation with fewer cases if incidents are dense; a comparative multi-site study may need many more. Report saturation reasoning and disconfirming efforts, not a fake power analysis.

Saturation-based sampling

Saturation means no new properties/dimensions are emerging for a category (in the Glaserian sense), not mere repetition of wordings. Track saturation by category, not only globally—some categories saturate early while others remain thin.

Integration tip

In proposals, distinguish initial purposeful sampling (who can get you started) from later theoretical sampling (who/what you need next as categories form). This shows methodological maturity in GT.

Checklist

• Sampling logic matches methodology (purposeful vs theoretical).
• Inclusion/exclusion criteria explicit and ethically justified.
• Referral/snowball bias considered and mitigated where possible.
• Saturation tracked with documented negative case searches.
• Limitations of non-probability sampling frankly acknowledged.

References (starting points)

• Patton, M. Q. Qualitative research and evaluation methods — purposeful sampling typology.
• Glaser, B. G., & Strauss, A. L. The Discovery of Grounded Theory — theoretical sampling origins.
• Emmel, N. Sampling and choosing cases in qualitative research.