Statistics in the News: Chapter 15 Analysis
Comparing the Effectiveness of Insect Repellents
Insect-transmitted disease remains a major source of illness
and death worldwide. To give just two examples, consider that
mosquitoes alone transmit disease to more than 700 million
persons each year, while malaria kills 3 million persons annually.
In the United States, thousands are falling victim to eastern
and western equine encephalitis and ever more people in ever
more states are being infected and die from the West Nile
virus, also transmitted by mosquitoes.
Protection against mosquito bites is best achieved by avoiding
infected habitats and wearing protective clothing, but that's
not feasible for everyone. That brings us to insect repellents.
In the United States, such readily available commercial products
include synthetic chemicals containing DEET (officially called
N,N-diethyl-3-methylbenzamide), various plant-derived essential
oils, and even repellent-impregnated moisturizers and wristbands.
Two researchers, Mark S. Fradin and John F. Day, recently investigated
which of these products provide reliable and prolonged complete
protection from mosquito bites. With the help of 15 volunteers,
they tested a number of alternative products in a controlled
laboratory environment, while holding constant the species of
the mosquitoes, their age, their degree of hunger, the humidity,
the temperature, and even the light-dark cycle.
Selected results from their two-way analysis of variance
(plus Tukey's HSD tests) are summarized in Table A.
TABLE A Protection Times of Insect Repellents
*Major ingredient DEET
Conclusion: DEET-based products provided complete
protection for the longest duration. Higher concentrations
of DEET provided longer-lasting protection. Botanical repellents
(based on cedar oil, eucalyptus oil, geranium oil, lemongrass
oil, peppermint oil, soybean oil, and such) provided less
protection. Repellent-impregnated wristbands offered no protection.
Source: Adapted from Mark S. Fradin and John F. Day,
"Comparative Efficacy of Insect Repellents Against Mosquito
Bites," The New England Journal of Medicine, July 4,
2002, pp. 13-18.
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