Observations tend to cluster around the median or mean
Empirical studies have demonstrated that it is typical for a large
number of the observations in any study to cluster near the
median. In right-skewed data this clustering takes place to the
left of (i.e., below) the median and in left-skewed data the
observations tend to cluster to the right (i.e., above) the median.
In symmetrical data, where the median and the mean are the same,
the observations tend to distribute equally around these measures
of central tendency.