Making Sense of Statistics for Family Practitioners: "The Spread"

Abstract

Quantitative data is traditionally summarised by two measures: a measure of the centre (average) of a data set and one of spread around this central point. In the previous article we noted that there are four useful measures for depicting the centre of a set of data namely the "arithmetic mean", "median", "mode" and "geometric mean". For the spread of a data set around the central point,there are three measures that are commonly used viz. the range, inter-quartile range and standard deviation.