Theoretical Saturation

The point in Grounded Theory data collection at which sampling additional cases yields no new categories, properties, or relationships in the developing analytic framework. Reaching saturation is the methodological criterion for stopping data collection; before saturation the theory is incomplete, after it further data are redundant for the current analysis.

Origin and strict sense

Glaser and Strauss (1967) tied saturation to theoretical sampling: cases are selected on the basis of analytic gaps, and saturation is achieved category by category as those gaps close. The category, not the dataset as a whole, is the unit being saturated. Each property of a category — its dimensions and the conditions under which it varies — must be theoretically saturated before the category itself is treated as complete.

Loose senses

The term has spread well beyond grounded theory and is often used to mean "we kept collecting data until we stopped hearing new things," sometimes called data saturation or thematic saturation. Researchers in this looser sense report a sample size and a claim that saturation was reached, often without theoretical sampling, without a coding system aimed at category development, and without a clear unit at which saturation is being asserted. Methodologists (including Braun and Clarke) have argued that such uses are conceptually incoherent and that researchers using thematic analysis should not invoke saturation at all.

Operationalising

When saturation is taken seriously, the researcher records when a new case last contributed a new code, property, or relationship to a given category, and continues sampling along the dimensions where contribution is still occurring. Reporting conventions ask for the unit being saturated, the sampling logic, and the evidence that further cases would not change the framework rather than a generic appeal to "saturation was achieved."

Use in applied linguistics

Saturation is widely cited in interview-based studies of teachers and learners. Many such claims would not survive a strict grounded-theory reading: sample sizes are fixed in advance, theoretical sampling is rare, and the unit of saturation is left implicit.

References

• Glaser, B. G., & Strauss, A. L. (1967). The Discovery of Grounded Theory: Strategies for Qualitative Research. Aldine.
• Charmaz, K. (2006). Constructing Grounded Theory: A Practical Guide Through Qualitative Analysis. SAGE.