Fig. 2

Boxplots showing the distribution of site performances for each outcome. Legend: The main body of a boxplot (coloured box) covers the range between the lower and upper quartiles. The white vertical line shows the position of the mean. The lines (whiskers) outside the boxes are extended as to cover all data points that lie within ±1.5 IQR (interquartile range, which is the difference between the upper and lower quartiles) form the upper and lower quartiles respectively. The dots indicate the points falling beyond the whiskers and they are usually considered to be outliers (the boxplot were constructed in STATA. A more detailed analysis of boxplot can be found in [20])