Standard deviation in muscle fiber cross sectional area (CSA). Box and whisker plot showing that radiation treatment caused a significant (p<.001) increase in the SD of muscle fiber CSA. Boxes depict the interquartile range (IQR), with a line at the median. Whiskers extend to the last observation within 1.5x the IQR. The closed circles are observations beyond 1.5x the IQR. Y = Young Adult Control; YR = Young Adult Radiated; O = Old Control, OR = Old Radiated.