“…Two measures of dispersion will be considered: the variance a; of y, and the interquartile range yo75 -yo.25 of y, where yo,75 and yo,25 represent the 0.75 and 0.25 quantiles of y. The variance is the best known measure of dispersion, and the interquantile range is widely used as a summary of dispersion in box plots (e.g., Helton et al, 1996;Sargent, 1996). The interquartile range is less sensitive to outliers than the variance, as is the case in the analogous situation for medians and means.…”