Russel-Research-Method-in-Anthropology

Research Design: Experiments and Experimental Thinking 125
In the 1950s, physicians began general use of the Pap Test, a simple office
procedure for determining the presence of cervical cancer. Figure 5.2 shows
that since 1950, the death rate from cervical cancer in the United States has
30
20
10
1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995
Figure 5.2. Death rate from cervical cancer, 1930–1995.
SOURCE: Adapted from B. Williams, A Sampler on Sampling, figure 2.1, p. 17. Reprinted with permission of
Lucent Technologies Inc./Bell Labs.
dropped steadily, from about 18 per 100,000 women to about 11 in 1970, to
about 8.3 in 1980, to about 6.5 in 1995 and to about 4.6 in 2000. If you look
only at the data after the intervention (the one-shot case study X O design),
you could easily conclude that the intervention (the Pap Test) was the sole
cause of this drop in cervical cancer deaths. There is no doubt that the continued
decline of cervical cancer deaths is due largely to the early detection provided
by the Pap Test, but by 1950, the death rate had already declined by
36% from 28 per 100,000 in 1930 (Williams 1978:16).
Never use a design of less logical power when one of greater power is feasible.
If pretest data are available, use them. On the other hand, a one-shot case
study is often the best you can do. Virtually all ethnography falls in this category,
and, as I have said before, nothing beats a good story, well told.
The One-Group Pretest-Posttest
The one-group pretest-posttest design is shown in figure 5.1f. Some variables
are measured (observed), then the intervention takes place, and then the
variables are measured again. This takes care of some of the problems associated
with the one-shot case study, but it doesn’t eliminate the threats of history,
testing, maturation, selection, and mortality. Most importantly, if there
is a significant difference in the pretest and posttest measurements, we can’t
tell if the intervention made that difference happen.
The one-group pretest-posttest design is commonly used in evaluating training
programs. The question asked is: Did the people who were exposed to this