Russel-Research-Method-in-Anthropology

56 Chapter 2
Determining Validity
You may have noticed a few paragraphs back that I casually slipped in the
statement that some scale had already been determined to be a valid instrument.
How do we know that the scale is measuring weight? Maybe it’s measuring
something else. How can we be sure? Since we have to make concepts
up to study them, there is no direct way to evaluate the validity of an instrument
for measuring a concept. Ultimately, we are left to decide, on the basis
of our best judgment, whether an instrument is valid or not.
We are helped in making that judgment by some tests for face validity,
content validity, construct validity, and criterion validity.
Face Validity
Establishing face validity involves simply looking at the operational indicators
of a concept and deciding whether or not, on the face of it, the indicators
make sense. On the face of it, asking people ‘‘How old were you when you
were toilet trained?’’ is not a valid way to get at this kind of information. A
paper-and-pencil test about the rules of the road is not, on the face of it, a
valid indicator of whether someone knows how to drive a car. But the paperand-pencil
test is probably a valid test for determining if an applicant for a
driver’s license can read road signs. These different instruments—the road test
and the paper-and-pencil test—have face validity for measuring different
things.
Boster (1985) studied how well the women of the Aguaruna Jívaro in Peru
understood the differences among manioc plants. He planted some fields with
different varieties of manioc and asked women to identify the varieties. This
technique, or instrument, for measuring cultural competence has great face
validity; most researchers would agree that being able to identify more varieties
of manioc is a valid indicator of cultural competence in this domain.
Boster might have simply asked women to list as many varieties of manioc
as they could. This instrument would not have been as valid, on the face of it,
as having them identify actual plants that were growing in the field. There are
just too many things that could interfere with a person’s memory of manioc
names, even if they were super competent about planting roots, harvesting
them, cooking them, trading them, and so on.
Face validity is based on consensus among researchers: If everyone agrees
that asking people ‘‘How old are you’’ is a valid instrument for measuring age,
then, until proven otherwise, that question is a valid instrument for measuring
age.