Theoretical saturation

A topic in research methodology

Theoretical saturation is a key concept in grounded theory studies.

"Theoretical saturation: The point in category development at which no new properties, dimensions, or relationships emerge during analysis."

Strauss & Corbin, 1998: 143

Confirmatory research uses designs that set out the data needed for analysis to answer the research questions. However, Researchers undertaking exploratory studies (discovery research) cannot know in advance what data will be needed to develop a theory sufficient to explain a situation. Often the data collected is determined by resources – e.g., the time the researcher can spend in field.
In grounded theory (GT) the study should continue until the theory is saturated and no further theoretical sampling is indicated:

"GT is only considered as ready for publication once theoretical saturation is reached. That is when new data collection (indicated by theoretical sampling) does not lead to any further changes to the theory, as the scheme of categories and their properties and relationships fit new data without further modification."

Taber, 2013: 103

During the grounded theory analysis the focus shifts as the analysis proceeds – from substantive to theoretical categories, the the relationships between those categories…

"As the analyst develops several workable coded categories, he/she should begin early to saturate as much as possible those that seem to have explanatory power."

Glaser & Holton, 2004, ¶54

Closure may not be permanent…

Karl Sabbagh wrote a book based on his investigation of a story of suspected scientific fraud. In the book he tells how he thought he had exhaused all the available source of substantive relevant information – a descriptoin that seems to fit 'theoretical saturation'

"…I had reached the point where

  • each new piece of information I gathered was adding less and less to the picture…and
  • what little was added was consistent with the overall picture I had already formed.

But to my surprise…two new 'caches' of documents came to light…"

Sabbagh, 2016/1999 (bullet point format added for emphasis)

Sabbagh described how new evidence came to his attention as he thought he was finalising his book. And then the publication of the book led to his being made aware of a further set of documents he had not previously found (actually in a Museum he had approached, but where the existence of the documents was only known by someone who had not been asked at the time, but later read the book.)

However, we cannot delay reaching conclusions, and publishing our work in the expectation (or fear) that more information will become available – but must make a sensible decision about when saturation is reached – whilst retaining the scientific attitude that all conclusions are open to being revisited in the light of new evidence.

Sources cited:

My introduction to educational research:

Taber, K. S. (2013). Classroom-based Research and Evidence-based Practice: An introduction (2nd ed.). London: Sage.

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