Russel-Research-Method-in-Anthropology

Qualitative Data Analysis II: Models and Matrices 525
Figure 18.2. An ethnographic decision model after interviewing two informants (Alex
and Sheila).
early classes probably won’t require more than 20 informants. Building an
EDM that accounts for this decision on two very different campuses—say,
a small, private college and a huge state school—may take twice that many
informants. As the culture gets more heterogeneous, the sample size needed
in order to find a stable decision model goes up. Accounting for the decisions
of students in New York City and Sussex, England, will require more interviews.
Add Mexico City and the number may double again. Add
Cameroon. . . .
Testing an EDM
Figure 18.3 may account for all the decisions of your next several informants,
but eventually you’ll run into an informant who says she doesn’t
always go to class, she wasn’t sick this morning, she doesn’t have a tough
class at 8 a.m., she wasn’t out late last night, and she still didn’t make her
early class today. Why? Because she just didn’t feel like it.
If you add enough constraints, you can always build a model to account for
every decision of every respondent. But what’s the use of a model with 20
different sets of ordered reasons that accounts for the decisions of 20 informants?
You might as well just ask every informant to explain his or her
actions. The trick is to model the decisions of, say, 18 out of 20 informants