As repellents were purchased, they were labeled sequentially from
1 to 16. A random-number generator was then used to determine
the order in which the products would be tested on each subject.
A total of 720 individual tests were conducted, with each repellent
being tested three times on each subject. Most subjects only
completed one test per day. The average time to completion of
all three tests was 10.2 days. In the case of repellents that were
identified as very short-acting in the initial test, subjects were permitted
to conduct all three tests of the repellent in a single day,
washing the skin with an unscented soap before each application
of the repellent. Subjects did not test more than one repellent
product on a single day. No information on the likely duration of
action of each repellent was provided to subjects before they began
their tests.