Russel-Research-Method-in-Anthropology

Sampling 153
116. If the first random number between 1 and 3 is 3, go to column 3. If the
first random number between 1 and 96 is 43, count down 43 lines. Decide if
the listing is eligible. It may be a blank line or a business. That’s why you
generate 400 sets of numbers to get 200 good listings.
Telephone books don’t actually make good sampling frames—too many
people have unlisted numbers (which is why we have random digit dialing—
see chapter 10). But since everyone knows what a phone book looks like, it
makes a good example for learning how to sample big, unnumbered lists of
things, like the list of Catholic priests in Paraguay or the list of orthopedic
surgeons in California.
Stratified Sampling
Stratified random sampling ensures that key subpopulations are included
in your sample. You divide a population (a sampling frame) into subpopulations
(subframes), based on key independent variables and then take a random
(unbiased), sample from each of those subpopulations. You might divide the
population into men and women, or into rural and urban subframes—or into
key age groups (18–34, 35–49, etc.) or key income groups. As the main sampling
frame gets divided by key independent variables, the subframes presumably
get more and more homogeneous with regard to the key dependent variable
in the study.
In 1996, for example, representative samples of adult voters in the United
States were asked the following question:
Which comes closest to your position? Abortion should be . . .
Legal in Legal in Illegal in Illegal in
all cases most cases most cases all cases
Across all voters, 60% said that abortion should be legal in all (25%) or
most (35%) cases and only 36% said it should be illegal in all (12%) or most
(24%) cases. (The remaining 4% had no opinion.)
These facts hide some important differences across religious, ethnic, gender,
political, and age groups. Among Catholic voters, 59% said that abortion
should be legal in all (22%) or most (37%) cases; among Jewish voters, 91%
said that abortion should be legal in all (51%) or most (40%) cases. Among
registered Democrats, 72% favored legal abortion in all or most cases; among
registered Republicans, 45% took that position (Ladd and Bowman 1997:44–
46). Sampling from smaller chunks (by age, gender, and so on) ensures not