variable (typically a treatment or independent variable) to another. The third
function, reduction of dimensionality, continues to be less commonly utilized
than the first two. This final category includes methods for reducing the
number of variables in a system while only minimally reducing the amount
of information, therefore making a problem easier to visualize and to under-
stand. Examples of such techniques are factor analysis and cluster analysis.
A subset of this last function, discussed later under descriptive statistics, is
the reduction of raw data to single expressions of central tendency and
variability (such as the mean and standard deviation).