ABSTRACT
Many variables in the social sciences are distributions, and one important feature of a distribution is variability—the spread or dispersion in the scores in the distribution. Looking at the range of a distribution of scores helps to define the variability in that distribution. The interquartile range is a further way to specify the variability in a distribution. This chapter compares self-reported preinjury physical frailty measures with proxy-reported measures. The interquartile range is the difference between the 25th and 75th percentile. It contains the middle 50" of the distribution. The median falls exactly between the 25th percentile and the 75th percentile, so the median is in the middle of the interquartile range. The interquartile range is helpful to know because it reveals the dispersion of the middle 50" of the distribution. The Life Space Assessment (LSA) examines an individual's usual patterns of mobility during the month preceding assessment.
