Effect of iron supplementation on change in serum indicators.

Box plots indicate 25th and 75th percentiles (box) and the median (thick line across each box). Vertical lines indicate highest and lowest values, excluding outliers (5 largest and 5 smallest values). Group sample sizes are indicated in parentheses; Pvalues indicate the level of significance when testing for differences in distributions relative to children receiving placebo (Mann-Whitney test). See “Statistical analysis” for further explanation.