Fig. 2From: The state of asthma epidemiology: an overview of systematic reviews and their quality Box plots of AMSTAR scores over periods of publication. The lower box margin indicates the 1st quartile; the upper box margin indicates the 3rd quartile. The vertical line within the box indicates the median. Whiskers are drawn at the most extreme value within a distance of 1.5-times the interquartile range from the respective box margin. Multiple outliers at the same value are jitteredBack to article page