Standardization menu

This allows a user to choose between three different methods
used to standardize the view of the data.

Note: These choices apply to all the data, not just to the
currently selected variables; that is, if new variables are
subsequently selected for plotting, the same standardization
method will be used.

Min/Max:  Each variable is centered at the
  midpoint of the variable group to which it belongs.

Mean/StdDev:  Each variable is scaled using the mean
  and standard deviation of the variable group to which
  it belongs.

Median/MAD:  Each variable is scaled using the median
  and median absolute deviation of the variable group to
  which it belongs.

The scrollbar affects the second two data standardization
methods.  It controls the scaling of the plot by increasing or
decreasing the number of deviations (either standard deviation
or median absolute deviation) contained within the plotting
window.