Theoretical saturation
Theoretical saturation is the point in a grounded theory study at which new data no longer adds properties to the categories being developed, so the researcher can stop collecting data on them. Barney Glaser and Anselm Strauss introduced the idea in 1967.
How it works
In grounded theory, sampling is theoretical: each new participant is chosen to fill out a category or test a relationship the analysis has raised. A category is saturated when further cases only repeat properties already found. Glaser and Strauss described the researcher seeing similar instances over and over until they become empirically confident the category is complete.
Theoretical saturation is narrower than data saturation, which is about new information of any kind. It concerns the development of theory, category by category. Researchers have also distinguished code saturation, hearing no new codes, from meaning saturation, fully understanding each code, which usually takes more interviews.
A worked example
Sales staff at a department store chain are resisting a new scheduling system, and a researcher studying why has a category, "loss of control". After interviews with sales associates, she samples floor managers and stockroom staff to test it. Interviews 21 to 26 add no new properties, only repeats, so she treats the category as saturated and turns to the next one.
Related
Automate this in Pulse
When an emerging category points to a new group, a researcher can write a short Pulse brief for that group alone, the move theoretical sampling calls for.