‘Are we there yet?’ Saturation in qualitative research and how to use it

Written by Dr Ben Saunders

I think I speak for most qualitative researchers when I say saturation is taken for granted, yet there continues to be inconsistency in how it’s used and even uncertainty on how to use it. Drawing on our recently published paper, this blog tackles the ‘what, where, when, why and hows’ of using saturation in research.

What is Saturation?

In short, saturation is used as a criterion for qualitative researchers to decipher when data collection or analysis is discontinued — in essence they reach ‘saturation point’. But this is research methodology we’re talking about, so it’s never going to be short and sweet.

From analysing existing literature, we’ve been able to identify four approaches to saturation, which may be either inductive (exploratory — finding patterns of explanations/theories) or deductive (using data to test pre-determined theories);

Theoretical saturation (inductive)

Data analysis leads to well-developed theories where no aspects remain hypothetical. The researcher(s) reaches the decision that no further data collection is needed.

Inductive thematic saturation

Similar to theoretical saturation, but it focusses on the identification and number of ‘new’ codes and themes rather than the completeness of theoretical categories.

A priori thematic saturation (deductive)

Establishing whether there is enough data to illustrate a pre-determined theoretical category.

Data saturation

Moving away from data analysis, this is based on how much data (i.e. the number of interviews) are needed until you’re no longer finding anything new.

Where and why should we use saturation?

The role of the theory is hugely influential to the relevance and meaning of saturation. In both deductive and inductive approaches, we are able to make sense of the role of saturation because of the underlying approach to the analysis being thematic. It will usually occur in interview or focus group studies that involve a number of informants.

It’s less straightforward in studies based on biographical or narrative approaches to analysis because they focus exclusively or predominantly on the accounts of an individual (e.g. interpretative phenomenological analysis). It might appear that saturation indicates completeness of a biographical account, but this is questionable. Can saturation usefully describe a participant’s story as ‘complete’ given the distance that it moves us away from the use of saturation in thematic approaches? Surely this would stretch the coherence and utility of saturation too widely?

When and how?

Perspective will have a big implication on when saturation should be sought. Saturation can be identified early on if you take the ‘data saturation’ or/and ‘inductive thematic saturation’ approach. Data saturation will rely on the researcher’s perspective on what they’ve heard during interviews to decide whether further data collection is needed. Inductive thematic saturation looks for the (non)emergence of codes or themes.

In contrast, theoretical saturation is reached much later, often when grounded theory categories has been developed, so analysis is much more advanced.

Straus and Corbin quite rightly highlighted the issues with identifying the point of saturation and whether it’s just a cumulative judgement. Although it’s commonly seen as a discrete event, there will always be the potential for ‘new’ codes or theories to emerge. Analysis will therefore not suddenly become ‘rich’ or ‘insightful’ after the addition of one interview, rather it becomes ‘richer’ or ‘more insightful- raising the question ‘how much saturation is enough’ rather than ‘has saturation occurred’.

Attempting to identify the right point of saturation perhaps reflects the uncertainty of how to use it. Determining whether further data collection or analysis is needed, based on the data already gathered, essentially refers to the unobserved based on the observed — an uncertain predictive claim which can only be tested if the decision to halt data collection is overturned.

So, if saturation is unpredictable, what’s our advice?

Here are our top 4 points to consider when using saturation in your research….

Define its purpose

The relevance of your saturation and its meaning will depend on the role of the theory and the analytical approaches you’ve adopted etc. Therefore, it may serve different purposes for different types of research — purposes that need to be clearly articulated by the researcher.

Don’t saturate your saturation

There needs to be a limit on your range of purposes for saturation, or else you run the risk of stretching or diluting its meaning to the point where it becomes too widely encompassing.

Event or an ongoing process?

When to use saturation, and how you reach saturation will differ depending on the type of study. Assumptions about whether it represents a distinct event or ongoing process will also differ.

Recognise its inconsistencies

If anything, this paper confirmed the need for a more transparent reporting of saturation, as well as a thorough re-evaluation of how it’s considered and used — including the recognition of potential inconsistencies and contradictions in its use. Considering the four different types of saturation outlined earlier will help serve as a guide for this.

The blog was adapted from the following paper:

Saunders, B., Sim, J., Kingstone, T., Baker, S., Waterfield, J., Bartlam, B., Burroughs, H. and Jinks, C. (2017). Saturation in qualitative research: exploring its conceptualization and operationalization. Quality and Quantity. https://doi.org/10.1007/s11135-017-0574-8.