sample size needs to be justified and Odds ratio should be reported with 95% confidence interval 3 February 2016 Siddharudha Shivalli, Yenepoya Medical College, Yenepoya University, Mangaluru, Karnataka, India I read this article by Nzobo BJ et al with a great interest. Authors’ efforts are praiseworthy. In their school based cross section study, authors report the Prevalence of asymptomatic malaria infection and use of different malaria control measures among primary school children in Morogoro Municipality, Tanzania. However, following are some issues and concerns. For a cross sectional study, adequacy and representativeness of study sample size are essential to ensure the validity of the study findings. In this study, multistage cluster sampling method was used. Morogoro municipality was divided into 5 geographical clusters and one school form each cluster was selected by random sampling. From each school one representative class (from standard 1–6) was selected. Finally, by random sampling technique 70 children were selected. However, how did the authors decide to select 70 children from each school? Why only one representative class children from each school? Authors should have calculated the sample size based on the following: total number of primary school children, reported prevalence of asymptomatic malaria (14.3%, reference :6 in the article), 5% confidence limit, 95% confidence level, design effect of 1.5 (owing to multistage cluster sampling) and anticipated non-response (e.g. 10-15%). And instead of one representative class, proportional selection based on age wise distribution in each school would have been more apt. Authors have used a structured and pre-tested questionnaire was used to collect information on demographic characteristics, knowledge about the transmission and prevention of malaria, ownership, and utilization of ITNs, and use of ACT of all 317 out of 350 eligible participants. However, is it necessary and possible to assess the knowledge about the transmission and prevention of malaria, and use of ACT among school children aged 6–13 years? Moreover, assessed knowledge about the transmission and prevention of malaria is not reflected in result section. It is recommended that Odds ratio should be reported with 95% confidence interval while expressing the strength of association. None the less, we must congratulate the authors for investigating an important public health problem. Competing interests The author declares that there is no conflict of interest about this publication.