The investigators calculated a sample size of 54 patients in each group for 90% power and 95% confidence. In the calculation, the researchers assumed that the children receiving intrarectal quinine would have a mean parasite clearance time of 39.9 (SD 24.3) hours and those receiving intravenous quinine would have a mean parasite clearance time of 55.0(SD 24.3) hours (27.5% effect size), according to a study by Aceng, Byarugaba and Tumwine in the same hospital.