Total DNA yield as a function of collection year from 120 ACCORD buffy coat specimens. The figure shows a Tukey boxplot of variation in DNA yield for each year of blood collection in the 120 ACCORD samples. The upper and lower edges (hinges) of the boxes are the third and first quartiles and the central line shows the median value of yield for a year. The lines radiating above and below the boxes visually show the range to the maximum and minimum yields. There are no outlier samples in any of the years with unusually large or small yields as defined by the usual robust test of more than 1.5 × interquartile range.