Qualitative Research: Sampling

Purposive and Theoretical Sampling:

When identifying means for recording data, one must be wary in qualitative research to how they collect data as well, it can be via unstructured or semi-structured observations and interviews, documents, and visual materials (Creswell, 2014).  Purposeful sampling is to help select the (1) actors, (2) events, (3) setting, and (4) process that will best allow the researcher to get a firm grasp at understanding and addressing their central questions and sub-questions in their study.  Also, consider how many sites and participants there should be in the study (identifying your sample size).  The sample size can vary from 1-2 in narrative research, 3-10 in grounded theory, 20-30 for ethnographic studies, and 4-5 cases in case studies (Creswell, 2014).

However, you can reach data saturation (when the research stops the data collection because there exists no more new information that would reveal any other insights or properties addressing the question of the research) before any of these aforementioned numbers (Creswell, 2014). Theoretical sampling is theoretically bound around a concept, but this type of sampling touches more on this concept of data saturation.  Thus, when the researcher is trying to understand the data in order to help them define or understand their theory to the point of data saturation, rather than reaching a defined number.


An example of this could come from studying the effects of business decisions affecting the family through analyzing relocation decisions on non-military families. (PROCESS)  Purposefully I would like to sample in this example are three groups of families, ACTORS: those with no children, those with children that are no older than 12 years of age, and those with one or more children over the age of 13.  I want to see if there is a difference between the reactions based on having kids and having kids that are older versus younger, over the past decade (EVENT) at Boeing (SETTING).  I could aim for 20-30 families per group to a total of 60-90 sample size, or I could aim for data saturation between each of these groups (Theoretically sampling).  If I want to stick with 60-90 as a total sample size, I could aim for an open answer survey or conduct interviews (which is more costly on my end).  If I wish to aim for data saturation, it can be more easily done with interviews.


Observational protocol and qualitative documentations

As a researcher, you could be a non-participant to a full-on participant when observing your subjects in a study.  Thus, the observed/empathized behavioral and activities of individuals in the study are jotted down in field notes (Creswell, 2013).  Most researchers use an observational protocol to jotting down these notes as they observe their subjects.  According to Creswell (2013), this protocol could consist of: “separate descriptive notes (portraits of the participants, a reconstruction of dialogue, a description of the physical setting, accounts of particular events, or activities) [to] reflective notes (the researcher’s personal thoughts, such as “speculation, feelings, problems, ideas, hunches, impressions, and prejudices), … this form might [have] demographic information about the time, place, and date of the field setting where the observation takes place.”

Whereas, observational work can be combined with in-depth interviewing, and sometimes the observational work (which can be an everyday activity) can help prepare the researcher for the interviews (Rubin, 2012).  Doing so can increase the quality of the interviews because the interviewers know what the researcher has seen or read and can provide more information on those materials.  This can also allow the researcher to master the terminology before entering the interview. Finally, Rubin (2012) also states that cultural norms become more visible through observation rather than just a pure in-depth interview.

In Creswell (2013), Qualitative Documents are information contained within documents that could help a researcher out in their study that could be either public (newspapers, meeting minutes, official reports) and/or private (personal journals/diaries, letters, emails, internal manuals, written procedures, etc.) documents.  This can also include pictures, videos, educational materials, books, files. Whereas, Artifact Analysis is the analysis of the written text, usually are charts, flow sheets, intake forms, reports, etc.

The main analysis approach of this document would be to read the document to gain a subject matter understanding.  Document analysis would aid in quickly grouping, sorting and resort the data obtained for a study.  This manual will not be included in the coded dataset, but will help provide appropriate codes/categories for the interview analysis, in other words give me suggestions about what might be related to what.   Finally, one way to interpret this document would be for triangulation of data (data from multiple sources that are highly correlated) between the observation, interviews and this document.