If you are given an instruction to “describe” a set of data, be sure you discuss the shape of the data
(including gaps and clusters in the data), the center of the data (mean, median, mode), and the spread of
the data (range, interquartile range, standard deviation).
Graphical Analysis
Our purpose in drawing a graph of data is to get a visual sense of it. We are interested in the shape of the
data as well as gaps in the data, clusters of datapoints, and outliers (which are datapoints that lie well
outside of the general pattern of the data).
Shape
When we describe shape , what we are primarily interested in is the extent to which the graph appears to
be symmetric (has symmetry around some axis), mound-shaped (bell-shaped ), skewed (data are
skewed to the left if the tail is to the left; to the right if the tail is to the right), bimodal (has more than one
location with many scores), or uniform (frequencies of the various values are more-or-less constant).
This graph could be described as symmetric and mound-shaped (or bell-shaped) . Note that it doesn’t
have to be perfectly symmetrical to be classified as symmetric.
This graph is of a uniform distribution. Again, note that it does not have to be perfectly uniform to be
described as uniform .