Russel-Research-Method-in-Anthropology

296 Chapter 10
If you run through this process with a sufficiently large, representative sample
of a population, and if people cooperate and answer all questions truthfully,
then you can calculate the percentage of the population that answered
‘‘yes’’ to question A. Here’s the formula:
P A or B (P A P A ) (P B P B ) Formula 10.2
The percentage of people who answer ‘‘yes’’ to either A or B (the percentage
of people who answer ‘‘yes’’ to question A) times (the percentage of times that
question A is asked) plus (the percentage of people who answered ‘‘yes’’ to question
B) times (the percentage of times question B is asked).
The only unknown in this equation is the percentage of people who
answered ‘‘yes’’ to question A, the sensitive question. We know, from our data,
the percentages of ‘‘yes’’ answers to either question. Suppose that 33% of all
respondents said ‘‘yes’’ to something. Since respondents answered question A
only if they chose a number from 1 to 4, then A was answered 40% of the time
and B was answered 60% of the time. Whenever B was answered, there was a
50% chance of it being answered ‘‘yes’’ because that’s the chance of getting
a heads on the toss of a fair coin. The problem now reads:
.33 A(.40) .50(.60) or
.33 .40A .30
which means that A .075. That is, given the parameters specified in this
experiment, if 33% of the sample says ‘‘yes’’ to either question, then about
8% of the sample answered ‘‘yes’’ to question A.
There are two problems associated with this technique. First, no matter
what you say or do, some people will not believe that you can’t identify them
and will therefore not tell the truth. Bradburn, Sudman et al. (1979) report that
35% of known offenders would not admit to having been convicted of drunken
driving in a randomized response survey. Second, like all survey techniques,
randomized response depends on large, representative samples. Since the technique
is time consuming to administer, this makes getting large, representative
samples difficult.
Still, the evidence is mounting that for some sensitive questions—Did you
smoke dope in the last week? Have you ever bought a term paper? Have you
stolen anything from your employer?—when you want the truth, the randomized
response method is worth the effort (see Scheers and Dayton [1987],
Nordlund et al. [1994], and Clark and Desharnais [1998] for some examples).
Every time I read in the newspaper that self-reported drug use among adolescents
has dropped by such-and-such and amount since whenever the last