Making sense of purposive sampling for key informant interviews in qualitative research.

1. MAKING SENSE OF
PURPOSIVE SAMPLING
FOR KEY INFORMANT INTERVIEWS
PAIGHTON SMYTH
EDRD*6000
MARCH 9TH, 2018

2. OUTLINE
Understanding sampling
Purposive sampling
Opportunities
Challenges
Case Study
Let’s Discuss
References

3. SAMPLING SENSE
• Sampling is an area of qualitative research
that is overlooked (Marshall, 1996)
• Sampling causes confusion because of the
complex definitions & numerous variations
of types (Marshall, 1996)
• Sampling is key to designing effective and
applicable qualitative research (Marshall, 1996)

4. PURPOSIVE SAMPLING
• Purposive sampling relies on the
researchers’ knowledge of the research
field and connection with the targeted
audience (Barratt, Ferris, & Lenton,
2015)
• The researcher outlines the information
needed for the project (Tongco, 2007)
• The researcher seeks out the individuals
that poses certain qualities that allow
them to provide the information needed
(Tongco, 2007)

5. OPPORTUNITIES
• Unlike quantitative research, qualitative allows for less
emphasis on a large popular size and more on extracting
meaningful data from a source (Onwuegbuzie and Leech,
2007)
• Small sample sizes allow for detailed and intense interviews
with key informants (Onwuegbuzie and Leech , 2007)
• Utilizing purposive sampling encourages efficient data
collection and the researcher has control over the
recruitment process (Mammen & Sano, 2012)

6. CHALLENGES
The main problem associated with utilizing purposive
sampling in research methodology is that it decreases
the studies ability to represent a larger population.
A study by Barratt, Ferris and Lention (2015) found
that when using purposive sampling, their results
could not be used to estimate behaviors in a wider
population or have the ability to make strong
quantitative inferences.
Purposive sampling allows the choice of a specific
population, but finding key enough informants with
the key requirements may pose as a challenge.

7. CASE STUDY
Gaining Access to Economically Marginalized Rural Populations:
Lessons Learned from Nonprobability Sampling
The study found that the purposive sampling
method contributed significantly to the
knowledge base on rural, low-income
families.
The study did mention the drawback of the
inability to generalize this information to a
greater population due to the purposive
sampling method.
(Mammen & Sano, 2012)
A study utilized purposive sampling as one their methods
to access rural areas of the United States who
demonstrate persistent poverty rates.
The purposive sampling technique allowed access to
economically disadvantaged, rural mothers with a broad
range of lived experienced who were considered to be full
of information.
The study chose to access their specific population
through local organizations such as Housing Authority,
food pantries and survival centers. If one area of interest
did not generate enough participants, they simply moved
to the next.

8. LET’S DISCUSS
• Can you think of types of research projects
that would benefit from purposive sampling
when identifying key informants?
• As a CDE student preparing to perform
research, do you feel that the inability to
apply your research findings to a larger
population base, would cause you to not
choose purposive sampling?
• Do you believe that the case study identified
was correct in choosing purposive sampling
in the methodology? If not – what type of
sampling should they have chosen?

9. REFERENCES
Barratt, M., Ferris, J., & Lenton, S. (2015). Hidden populations, online purposive sampling, and external validity:
Taking off the blindfold. Field Methods, 27(1), 3-21. 10.1177/1525822X14526838 Retrieved
from http://resolver.scholarsportal.info/resolve/1525822x/v27i0001/3_hpopsaevtotb
Marshall, M. N. (1996). Sampling for qualitative research. Family practice, 13(6), 522-526.
Mammen, S., & Sano, Y. (2012). Gaining Access to Economically Marginalized Rural Populations: Lessons Learned
from Nonprobability Sampling. Rural Sociology, 77(3), 462–482. https://doi.org/10.1111/j.1549-
0831.2012.00083.x
Onwuegbuzie, A. J., & Leech, N. L. (2007). A call for qualitative power analyses. Quality & Quantity, 41(1), 105-121.
Tongco, M. D. C. (2007). Purposive sampling as a tool for informant selection. Ethnobotany Research and
applications, 5, 147-158.