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RESEARCH: Axel Kroeger, Audrey Lenhart, Manuel Ochoa, Elci Villegas, Michael Levy, Neal Alexander, and P J McCall Effective control of dengue vectors with curtains and water container covers treated with insecticide in Mexico and Venezuela: cluster randomised trials BMJ 2006; 332: 1247-1252 [Abstract] [Full text]

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Sample size calculation

Gabriela Salmon   (26 March 2009)

Re: Sample size calculation

Axel Kroeger   (27 March 2009)

Sample size calculation 26 March 2009
Gabriela Salmon, Student Johns Hopkins School of Public Health, MD 21202 Send response to journal: Re: Sample size calculation	Good afternoon, I am confused about the sample size calculation for this article. It is explained that nine pairs of clusters were a conservative amount because previously seven pairs had been calculated for a previous trial in Trujillo. However, looking over that other trial in Trujillo, the study was oriented to vector control for cutaneous leishmaniasis and does not provide a lot of detail about sample size calculations. Could you please clarify this issue? Sincerely, Gabriela Salmon-Mulanovich Competing interests: None declared
Re: Sample size calculation 27 March 2009
Axel Kroeger, Scientist WHO, Geneva,CH-1211 Send response to journal: Re: Re: Sample size calculation	At the time of our Mexico/Venezuela study on ITMs for dengue vector control we had no information on comparative studies. The only similar one was our CRT on sand flies in Venezuela.The sample size calculation was done following the Hayes & Bennet paper quoted in the dengue publication. Nowadays, several years later, we are able to do sample size calculations with much more precise assumptions based on this and other dengue vector trials. Competing interests: None declared