\noindent where
$
\mathbf{x}_{j}
$
is the
$
j^{\mathrm{th}}
$
column of a matrix
$
\mathbf{X}
$,
$
\bar{x}_{j}
$
is the mean of
$
\mathbf{x}_{j}
$,
and
$
s_{j}
$
is the standard deviation of
$
\mathbf{x}_{j}
$.
