Russel-Research-Method-in-Anthropology

Sampling 149
the potential sampling error in your study. (I’ll discuss how you know this
later on in this chapter.) When historical circumstances (the surprise court
judgment, for example) require it, you could interview the same sample of 60
again (in what is known as a panel study), or take another representative sample
of the same size and see what differences there are before and after the
critical event.
In either case, you are better off with the sample than with the whole population.
By the way, there is no guarantee that a week is quick enough to avoid
the problem described here. It’s just less likely to be a problem.
Sampling Frames
If you can get it, the first thing you need for a good sample is a good sampling
frame. (I say, ‘‘if you can get it,’’ because a lot of social research is
done on populations for which no sampling frame exists. More on this at the
end of this chapter.) A sampling frame is a list of units of analysis from which
you take a sample and to which you generalize.
A sampling frame may be a telephone directory, or the tax rolls of a community,
or a census of a community that you do yourself. In the United States,
the city directories (published by R. L. Polk and Company) are often adequate
sampling frames. The directories are available for many small towns at the
local library or Chamber of Commerce. Professional survey researchers in the
United States often purchase samples from firms that keep up-to-date databases
just for this purpose.
For many projects, though, especially projects that involve field research,
you have to get your own census of the population you are studying. Whether
you work in a village or a hospital, a census gives you a sampling frame from
which to take many samples during a research project. It also gives you a basis
for comparison if you go back to the same community later.
Simple Random Samples
To get a simple random sample of 200 out of 640 people in a village, you
number each individual from 1 to 640 and then take a random grab of 200 out
of the numbers from 1 to 640. The easiest way to take random samples is with
a computer. All of the popular program packages for statistical analysis have
built-in random-number generators. Some of the most popular include SAS,
SPSS, SYSTAT, KWIKSTAT, STATA, and STATMOST. (Internet
addresses for all these programs are given in appendix F.) You can also take a