Nonprobability Sampling and Choosing Informants


  1. Quota Sampling
  2. Purposive or Judgment Sampling
  3. Convenience or Haphazard Sampling
  4. Snowball Sampling
  5. Case Control Sampling
  6. Sampling and Credibility
  1. Choosing Informants
  2. Key Informants
  3. Selecting Culturally Specialized Informants
  4. The Cultural Consensus Model
  5. A Handy Shortcut
  6. Paying Informants


What it means
Where Used
Decide on subpops & proportions you want in sample and then go find them Polling, market research
Not unbiased but often a cost effective approximation to probability sampling
Purposive or Judgment 
Figure out who you need to talk to and go find them. No overall numbers/design.
Pilot studies, selection for case studies, participant observation

Convenience or Haphazard
Talk to whomever you run into.
Phenomenological research, exploratory, grounded theory.
Not for estimating pop parms from sample.
Talk to one informant, ask about referrals to others.
Network studies.  Hard to find populations.  Members of populations with social structure or network.
Can be biased toward the well-known or well connected
Case Control
Start with purposive sample and then match other cases on some criterion.
Epidemiology studies.



Least You Should Know

After working with this chapter you should be able to… …explain how in ethnography informant competence plays a role similar to a representative sample in survey research.
…explain what key informants are.
…suggest some general strategies for finding key informants.

Food for Thought

Recall that the initial distinction we made was between studying cases and studying cultures.  What is it about culture that makes the methods described in this chapater appropriate for its study?


Concepts, terms, vocabulary

case control design (181)
convenience sampling (181)
cultural consensus model (194)
pilot studies (182)
purposive/judgment sampling (181)
quota sampling (181)
similarity matrices (195)
snowball sampling (181)

M i l l s    H o m e    P a g e    *    M i l l s    S o c i o l o g y    *    S O C 9 1    *    D a n    R y a n