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

82 ASKING QUESTIONS
asking about tests used to detect possible cancers in women. This
series of questions asks about mammograms, Pap smears, and breast
examinations by a physician. All preventive activities tend to be
substantially overreported, but mammograms are more distinct
events and are reported more accurately than Pap smears and breast
examinations. Different study results vary in the degree of overreporting,
but mammograms are roughly overreported by 40 percent,
Pap smears and breast examinations by 100 percent or more.
The questions attempt to sequence the behavior in a way that improves
reporting accuracy.
Library Card Ownership
What is the best way to determine if a person owns a library card?
It might seem as though a straightforward question would work
best. Consider the question “Do you have a library card for the
Denver Public Library in your own name?”
On the surface, this question may appear nonthreatening, but
since reading is generally considered a desirable activity, library card
ownership is likely to be overstated. In fact, with this particular
question, people overstated library ownership by 10 to 20 percent
(Parry and Crossley, 1950).
For socially desirable behavior, the extent of overstatement depends
not only on the level of desirability and the wording of the
question, but also on the proportion of the population who have
not behaved in the socially desirable manner. Thus, the potential
for overstatement is greater on library card ownership than for seat
belt usage, since only a minority of adults have library cards. Figure
3.2 shows another approach that was used when trying to assess
library card ownership in the Chicago area.
This version attempted to reduce overreporting by asking additional
questions about attitudes toward library facilities and about
card ownership of other household members—thereby removing
the stress from one specific question. Yet even in this version there
was still 10 to 20 percent overreporting by all respondents. There