Russel-Research-Method-in-Anthropology

166 Chapter 6
Number of Househould Heads
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10 20 30 40 50 60 70 80
Age
Figure 6.2a. Distribution of the ages of Ticuna household heads.
SOURCE: Adapted from data in A. Oyuela-Caycedo and J. J. Vieco Albarracín, ‘‘Aproximación cuantitativa a
la organización social de los ticuna del trapecio amazónico colombiano,’’ Revista Colombiana de Antropología,
Vol. 35, pp. 146–79, figure 1, p. 157, 1999.
figure 6.2. Figure 6.2a shows the distribution of the ages of the household
heads in the sample; figure 6.2b shows the distribution of the number of children
in the households of the sample. Both curves look very normal—just
what we expect from variables like age and number of children (more about
normal distributions in chapter 7). If the sample of Ticuna household heads
represents what we expect from age and number of children, then any other
variables the research team measured are likely (not guaranteed, just likely) to
be representative, too.
How Big Should a Sample Be?
There are two things you can do to get good samples. (1) You can ensure
sample accuracy by making sure that every element in the population has an
equal chance of being selected—that is, you can make sure the sample is unbiased.
(2) You can ensure sample precision by increasing the size of unbiased
samples. We’ve already discussed the importance of how to make samples
unbiased. The next step is to decide how big a sample needs to be.
Sample size depends on: (1) the heterogeneity of the population or chunks
of population (strata or clusters) from which you choose the elements; (2) how