Asking Questions - The Definitive Guide To Questionnaire Design ...

102 ASKING QUESTIONS
To illustrate how the procedure works, suppose that out of a
sample of 1,000 respondents, 200 answered “yes” to the pair of
questions given above and 800 answered “no.” The expected number
of persons answering “yes” to the question about the month of
their birthday is approximately 25 (1,000 × .3 ÷ 12). This assumes
that birth dates are equally distributed over the twelve months and
that .3 of the respondents saw a blue bead. Thus, the net number
of people answering “yes” to the question on drunken driving is
200 − 25, or 175. The number of people who answered Question
A is approximately .7 × 1,000, or 700. The percentage of people
who admit being arrested for drunken driving is 175 ÷ 700, or 25
percent.
By using this procedure, you can estimate the undesirable
behavior of a group while fully protecting the anonymity of the
respondent. With this method, however, you cannot relate individual
characteristics of respondents to individual behavior. That
is, standard regression procedures are not possible at an individual
level. If you have a very large sample, group characteristics can be
related to the estimates obtained from randomized response. For
example, you could look at all the answers of young women and
compare them to the answers of men and older age groups. On the
whole, much information is lost when randomized response is used.
Even if the information obtained from randomized response were
error-free (and it is not), the loss of information has made this procedure
much less popular than it was when first introduced.
The accuracy of information obtained by randomized response
depends on the respondent’s willingness to follow instructions,
understand the procedure, and tell the truth in exchange for
anonymity. Unfortunately, for very threatening questions, such as
our example of drunken driving given earlier, there is still substantial
underreporting of socially undesirable behavior.
Randomized response is also not an appropriate procedure for
asking questions about socially desirable behavior, where it may
lead to even higher levels of overreporting than standard methods.
Randomized and anonymous response procedures are appropriate